When 36-year-old Shalane Flanagan victoriously persevered to cross the finish line in Sunday's New York City marathon, a minute ahead of her nearest competitor (three-time defending champion Mary Keitany of Kenya) she knew she'd defeated more than a fierce competitor.

The three-time Olympian had defeated her own demon--the Great "Almost" in her life, even as the clock was winding down on her running career.

The running goddesses had been at best fickle towards Shalane since her second-place finish in 2010 (her first of only two NYC marathons). She had endured a crushing fourth-place finish at her hometown Boston Marathon and didn't exactly light up Rio like running mate Usain Bolt did, finishing a disappointing sixth-place finish after which she defeatedly said, "That's all I have. That's what I am." A back fracture after that kept her out of the Boston Marathon and out of races until the NYC event. 

It was especially satisfying for Flanagan because she had repeatedly told the media how important this race was to her.

Having finally achieved her goal of winning a major US marathon, Flanagan may or may not retire. Whatever she decides, no one can take away the case study in perseverance that she laid out. 

You can show Olympian perseverance too by keeping these three science-backed truths in mind:

1. Know that developing mental toughness is a science-backed key to success.

Research indicates that mental toughness is the single most important factor for success, even above intelligence (or having glossy teeth).

A University of Pennsylvania researcher, Angela Duckworth, confirmed this in her study of West Point cadets. The first summer for the cadets includes a grueling series of dawn-to-midnight tests (known as "The Beast Barracks") intended to push the mental, physical, and emotional limits of the newbies. Duckworth found that those who survived the tests best were not the most gifted athletically or intelligence-wise. They were the ones with the most grit.

Cadets who were just one standard deviation higher on a test called the Grit Scale were 60 percent more likely to finish Beast Barracks than their peers.

Duckworth confirmed the correlation between grit and success across many other professions such as investment bankers, lawyers, doctors, painters, and journalists.

You don't have to be a West Point enrollee or a Wall Street wonder to develop similar mental toughness. Nor is mental toughness based on a genetically pre-determined mental condition. 

It's not a trait, it's a choice.

Duckworth's Grit Scale is based on two vectors: consistency of interest and perseverance of effort. Said another way, mental toughness comes from staying consistent in your drive to achieve a specific goal (not losing passionate interest in that goal) and then consistently putting in the effort to achieve that goal (using daily habits to help).

Not genetics, grit.

2. Know that persevering builds your skill set for the future.

Remembering this will help give you strength to carry on.

Biographical author Jim Tobin writes of how Franklin Delano Roosevelt handled his sudden onset of polio; it forged a skill set he'd apply to become one of the greatest leaders of the 20th century. He points out that the way Roosevelt used improvisation, experimentation, and perseverance in living with polio would ingrain skills that he directly applied to facing the challenges of The Great Depression and World War II. 

As Tobin wrote: "The way Roosevelt fought against his paralysis, trying one thing, then another when the first thing failed, and then a third, was perfectly reflected in his pragmatic response to the crises of his presidency."

3. Know just how debilitating worrying is.

Worry acts like a bludgeon on those trying to persevere. We all worry from time to time.  However, research indicates that it can quickly become a cycle of self-perpetuating negative thoughts that can hammer our likelihood to persevere. 

We move towards what we believe.

And this before you even get to the negative health consequences of excessive worrying.

Science also bears solutions though. Researchers at Penn State indicate the importance of identifying the object of worry, setting aside time to worry about it (no more than 30 minutes), and focusing on solutions during that time. This is in contrast to the common belief that you should push your worries aside and keep plowing through when trying to persevere.

More research indicates that suppressing your worry altogether is an impossible task and that those who try to do so end up even more distressed. Net. plan some time for productive worry, then don't worry about it.

So whatever race you're running, keep at it.  One mile, one event, one dream at a time.