Despite her terror of the ocean, mother-of-two Tamara Loiselle found the courage to dive in and save a drowning couple.

A rogue wave hit Tamara Loiselle like a truck, its salt water searing her eyes, filling her nose and throat and knocking the wind from her 115-pound body. Behind her lay a brilliantly white beach becoming crowded with onlookers; beyond her, two heads bobbed in the angry, roiling sea – a man and a woman who had gone past warning flags and been pulled into danger by deadly riptides. Tamara was breathless, alone and deeply afraid. "For a split second, I thought about my kids and that I could die trying to save these people," says the 43-year-old single mom. "But I sent those thoughts back to the beach, caught my breath and kept going."

Entering the treacherous surf was the last thing Tamara, a part-time teacher from Calgary, Alberta, had in mind when she and a friend took an early-morning walk on the last day of their Christmas vacation in 2014. In fact, she hadn't stuck much more than a toe in the sea since arriving in Cancun, Mexico. Open ocean terrified her, despite the fact that she was an amateur triathlete and a superb swimmer. "I grew up near pools and lakes and never felt comfortable in the ocean," she says. That discomfort metastasized into a bone-rattling fear in 2008 when she fell, fully clothed, from a 35-foot ocean cruiser into chilly Pacific waters and nearly drowned. "I saw my 7-year-old daughter screaming as I struggled to pull myself back on board. I didn't have the strength to do it, and I let go. I felt that this might be it for me," says Tamara, who managed to swim 200 feet back to shore.

She'd largely avoided ocean surf ever since – until that day six years later when terrifying screams pierced the morning quiet in Cancun. Instinct spurred Tamara and her friend, also a rookie triathlete, to sprint toward the water. "A handful of security guards from the condo complex had arrived with a reel of rescue rope and a hand-held flotation device," says Tamara. "But they weren't going in. I ran up to them and motioned that I could swim, that I could go out there."

Tamara Loiselle with children Sasha, 8, and Kristanna, 15, and the family dog, Toby.

Tamara saw from the guards' grim faces that they viewed it as a suicide mission. The look in her friend's eyes was one of stunned disbelief. "But I didn't consider backing out," says Tamara. "The guards looped the rope around me; I grabbed the life preserver and went in."

Against the odds, Tamara pulled the couple to safety. After news of her spectacular act spread virally around the globe, she was awarded the prestigious Mountbatten Medal for the most courageous rescue in the Commonwealth and named one of Time magazine's five Hero Moms of the Year.

But what made her do it? How was Tamara able to override her fear and be a hero when others couldn't? And if she had drowned in her attempt to save two total strangers, leaving her children motherless, would she still have been called courageous – or a fool?

Philosophers have long pondered the concept of courage – what it is, why it's important and how we can muster more of it. But only recently have researchers delved into the science and psychology of courageous behavior itself. What they're finding sheds light on the potential for gutsiness built into our brains and what we can do to help it blossom.

What makes a brain and a body brave?

Tamara's story is a familiar one to David Rand, Ph.D., associate professor of psychology at Yale University. He and colleague Ziv Epstein spent a year analyzing interviews with recipients of the Carnegie Hero Medal, which is awarded to individuals who risk their lives for others. "We learned that two things must happen if you are going to take heroic action," says Rand. "You must be willing to go with your immediate gut response. And your gut response must be to help."

What's not typically part of the heroic formula is courage. "Heroes tend to act impulsively, without even thinking about danger," says Rand. "In the moment, they tend to be fearless. Courage is being afraid but acting anyway."

In 2010, researchers at the Weizmann Institute of Science in Israel published the results of their study on what courage looked like from inside the brain. The mad-scientist method: They loaded snake-fearing subjects into MRI machines (which are tubular and confining), then monitored in real time how subjects' brains reacted when they performed a courageous act – namely, pushing a button that released a live, wriggling (though tethered) five-foot snake into the machine.

What the researchers witnessed was a tussle between two distinct regions of the brain. The subgenual anterior cingulate cortex (sgACC) lit up as each subject moved the snake closer; the more afraid the subject was while moving the snake toward himself, the more active this hub of "courage" neurons became. When a subject caved in to fear and sent the snake away by pushing another button, the sgACC quieted, and the amygdala – the area that triggers the "fight or flight" response when we are threatened or afraid – became more engaged.

"Fear is fundamental to survival," says study coauthor Uri Nili, Ph.D. "But the human brain makes us capable of overriding it to a certain point. When there's a strong motivation, the sgACC sends out orders to inhibit the amygdala's fear response."

So, are people like Tamara simply blessed with extra-bossy "courage centers" in their brains? Not quite, says Nili. It's more likely that they're better at controlling how the sgACC behaves. "Some of this is probably how their neurons are naturally hardwired. But it's also how they've been conditioned to respond to fear in the past," says Nili. "In a sense, the more you practice being courageous, the better you become at it."

For Tamara, that training started early. Her dad was a cowboy and entrepreneur, and her mom made sure Tamara and her sister got a solid foundation as swimmers. She recalls physically intervening in a fistfight between two guys in high school, and in 1999, she helped rescue people from a car wreck. And she spit in the eye of her own near-drowning by training for a triathlon – a swimming, biking and running event that pushes the limits of mental and physical endurance. "I was overweight and out of shape when I fell out of that boat, and I vowed that I'd never let myself be that weak and vulnerable again," she says.

By the time she was in Cancun, Tamara was primed for courageous action. "I knew I was physically capable of swimming out to those people. At moments, I was able to turn my fear into anger. I wasn't going to let the ocean take me down again," she says.

Are the rest of us chicken?

If you suspect you'd have been on the beach with Tamara's friend and the security guards while she battled the sea, don't be too hard on yourself. To some extent, that's natural. "We are not just individuals – we belong to a whole species that's driven to survive," says Daniela Schiller, Ph.D., associate professor of psychiatry and neuroscience at Mount Sinai Medical Center in New York City. "From that perspective, it makes sense that some of us are more courageous than others. That way, not everyone will jump into the water and die at once."

This doesn't mean we should spend our days on life's sidelines – not all courageous acts are death-defying, and many allow us to cultivate more meaningful lives. There's the courage it takes to ask your boss for a raise; the bravery a cancer patient finds in herself to move ahead with treatment; the guts Rosa Parks needed to act on her beliefs and sit where she wanted to sit on the bus. "Humans are adaptive creatures," says Schiller. "You can change how you experience fearful situations. Courage is something that can be developed."

Psychologists have learned a lot about this from working with patients who have phobias – extreme and sometimes irrational terror of things like airplanes, spiders and open spaces. One successful treatment, exposure therapy, gradually increases patients' contact with what frightens them. They learn relaxation strategies like deep breathing to help reduce their anxiety in the moment. "Patients learn how to inhibit their brains' fear response. At first it takes conscious effort, but then it becomes automatic," says Nili. He suspects that if he'd continued to expose subjects to his creepy "snake MRI," he'd have seen changes in brain activity that reflected a transition from courage to fearlessness in regard to the snake.

Of course, phobias often involve exaggerated fear. And while Nili's subjects knew intellectually that they were in no real danger of being harmed by the slithery snake, courageous action in the real world offers no such guarantees: Risk is generally real. That's where judgment comes in, and that's what distinguishes bravery from recklessness. Impulsively walking out on a well-paying job to pursue your dream of becoming an opera singer is likely a reckless choice if you have a family that depends on your income, for instance.

"Courage requires weighing risk against the potential benefits of pursuing a goal and having a plan for how you want to achieve that goal," says Cynthia Pury, Ph.D., professor of psychology at Clemson University in Clemson, SC. "Even in situations where people act very quickly, they seem to have a strategy in their heads." Along those lines, quitting work to pursue opera singing might be courageous if you've saved up funds in advance, have been taking lessons at night and plan to transition gradually into your new lifestyle.

"It makes sense that if you want to be more courageous, you train yourself to be wise," says Pury, "because a person with a high level of practical wisdom will be able to figure out which risks are worth taking."

Bravery on the beach

All things considered, events played out in the best possible way for everyone involved on that frightening day in Cancun. It wouldn't have been a favor to anyone if Tamara's friend, with weaker swimming skills, had braved the waves and ended up needing to be rescued, too. And those guards with no lifesaving training had little incentive to threaten the security of their families for the benefit of two foolhardy tourists.

Then, of course, there was Tamara. "Everything came together for me at that moment – physically, emotionally, mentally," she says. "I knew what they were feeling because of my own near-drowning. Standing on that beach, I heard an inner voice telling me I would be protected and that I should go."

Shortly thereafter, the couple she had saved reached out to her on Facebook. "You left the scene as if what you did was just normal, everyday life....[but] what you did was simply heroic," wrote the man. "Ever since the incident, we're feeling that this is added time...a gift to be able to live more."

The leap of faith affected Tamara, as well. "My life has definitely taken a different direction," she says. Shortly after her brush with death when she fell off the boat, she had mustered the courage to separate from her husband of nine years. "It was scary, but I knew it was something I had to do," she says.

Since the rescue in Cancun, "I now do a lot of speaking engagements. Public speaking was probably the one thing that scared me more than death!" she says. "The event also reconnected me with my love of writing. I just finished a book, Called to Courage, about how this experience has changed me." (She's currently seeking a publisher.)

One thing Tamara has not been doing: continuing to participate in triathlons. "There was something that wasn't at peace within myself that was driving me to compete. But now it's gone," she says. She pauses, then continues to reflect: "I'm single. I'm focused on my book. I may not know my ultimate destination, but I know what my next step will be."

4 ways to exercise your bravery "muscles"

"You build courage each time you choose to leave the safety of your comfort zone for the sake of something more important," says Margie Warrell, author of Brave: 50 Everyday Acts of Courage to Thrive in Work, Love and Life. Here, ways to train yourself to be more fearless:

Speak up: Does someone often take credit for your work? Are you dissatisfied in your relationship? Don't let fear of an awkward situation keep you silent. "If there's something you feel the need to say, chances are there's someone who needs to hear it," says Warrell.

Accept yourself: Too often, our fear of being rejected and not fitting in keeps us from putting our authentic selves out there. If you weren't afraid of what people would say, what would you do today?

Risk failure: Make a habit of trying things you're not 100% sure you'll succeed at, even when it's as simple as sampling a new recipe or auditioning for a part at your community theater.

Say yes to you: Don't let the fear of disappointing others keep you from doing what inspires you, whether that's going back to school or taking a daily run. "It can be an act of courage to say no to an invitation or another request to volunteer at school," says Warrell.