Being successful often boils down to a combination of talent and luck, but research has proposed another essential ingredient.

When Angela Duckworth began teaching math to New York City public school kids, she noticed the difference between students excelling and failing did not come not down to IQ. The pivotal question: “Who is succeeding here and why?” led Duckworth to study psychology, and it kickstarted her journey to define “grit” and ultimately led to the Grit Scale.

“Grit is passion and perseverance for long-term goals,” Duckworth outlined in her now-viral TED Talk. “Grit is having stamina. Grit is sticking with your future day in, day out—not just for the week, not just for the month, but for years, and working really hard to make that future a reality.”

Duckworth continued: “Talent doesn’t make you ‘gritty,’ there are many talented individuals who simply do not follow through on their commitments.”

Researching national spelling bee contestants and military cadets, Duckworth found that grit (and not social intelligence, health, or IQ) was usually the distinguishing factor that marked a person—and their eventual success—apart.

Now a psychology professor, Duckworth developed the Grit Scale, a 12-step test allowing individuals to uncover how gritty they are, with questions such as whether setbacks discourage you or if you lose focus easily. Unsurprisingly, the subject of grit has piqued the interests of athletes.

Oregon-based John O’Sullivan founded the “Changing the Game” project after three decades as a professional soccer player and coach. As a best-selling author, he has written extensively about instilling grit in young athletes. O’Sullivan believes that competing in triathlons helps develop grit as it provides moments of disappointment and failure.

“Perhaps you train well, but fail to post the time you want,” he says. “Perhaps you encounter a mechanical issue on the bike or have a bad transition. In these moments, the ability to pick yourself up and push through the disappointment is critical. If you encounter these situations often enough, you develop grit.

“You learn not to panic. You learn to push through,” O’Sullivan continues. “These are not only sports skills, they are also life skills. Nothing in sports comes easy, especially in triathlon.” USA Triathlon Level 1 Coach Duane Solem created Last Chance Fitness in Atlanta, Georgia, to help others approach the aging process with a healthy mindset. As an older triathlete, Solem applies the Grit Scale to his own training.

“My grit is pretty high. If I feel I can’t do a workout, I go and do it anyway, and find that as soon as the heart starts pumping, I’m back in the zone,” Solem says.

His clients can learn a lot from his attitude, too: “Triathletes who want to improve their athletic performance have more grit than those who are happy with where they are. High-grit people have something that grinds all day long: wanting more.

“I’ve found that most people who push into the really tough zone have one or many kinds of semi-rational states of mind that keep them going under tough conditions,” Solem says. That’s not to say gritty athletes do not appreciate their own accomplishments or fortune. In fact, Solem says, they must.

“By working harder and gaining a bit in one, even small, aspect of something they do, they will push their grit level up,” Solem says. “Push the limit, feel that tiny glow of satisfaction, and recognize that feeling of achievement and own it.”

As Duckworth put it in her famed TED Talk: “Grit is living life like it’s a marathon, not a sprint.”