Kevin Gonzalez, a 24-year-old from the South Bronx, had been training for the marathon his entire life — he just didn’t know it. Gonzalez didn’t regularly go on 18-mile training runs on the weekend nor did he spend hours on the treadmill; in fact, he wasn’t a runner at all. But his tough upbringing prepped him to endure a long haul, not just a sprint.

After a pre-dawn run, Gonzalez met with NationSwell recently in the front lobby of the Bowery Mission, a men’s residential recovery center in East Harlem, N.Y. After living at the shelter for a few months, Gonzalez signed up with Back on My Feet, a program that uses running to instill responsibility and self-sufficiency, with the ultimate goal of running the 2015 New York City Marathon. Gonzalez heard that the nonprofit’s morning runs had translated into 2,000 jobs and 1,400 housing placements for homeless participants, so he laced his running shoes to test whether he could be the organization’s next success story.

“I went from running the streets to running to save my life,” Gonzalez says. “Now I knew what I wanted to do and why it mattered. I had the dedication and a goal to achieve.”

That feeling of determination was new for Gonzalez, who was orphaned at a young age and spent his childhood in the foster care system. From age 17, he’s been on his own. With a minimum-wage job, Gonzalez was able to pay for his own apartment for a year before moving with his girlfriend’s family. Struggling with addictions — alcohol, drugs and cigarettes — he lost a job and was kicked out. Without anywhere to go, Gonzalez was living on the street.

His first run wasn’t easy. Another Back on My Feet member ran alongside Gonzalez for the whole hour to make sure he wasn’t alone. But that guy wanted to chat, something that Gonzalez, who was struggling to breathe, found impossible. Six months since he started, a morning run has become part of the routine, and Gonzalez’s lungs have greater capacity.

“Nothing is as relaxing as breaking a quick sweat,” Gonzalez says. “It helps with my stress and anxieties. I feel like I’m 18 again. I’m in the best shape of my life.”

The weekend before the Big Apple’s marathon last month, on one of his final practice workouts, Gonzalez stumbled and sprained his ankle. He had trained so hard and the injury didn’t seem that bad, so Gonzalez continued with his marathon plan. With his toe on the starting line in Staten Island, his shoulders were tense with nervousness. Using the resilience he’d built and strengthened over so many years, Gonzalez pushed his worries about the injury aside.

When he passed the 18th mile and saw the cheering supporters from the shelter at 110th Street, he knew he could make it. Four and a half hours after starting, he crossed the finish line in Central Park.

With one marathon down, Gonzalez already has his sights on his next one. He now has a job walking dogs, and he expects to enroll in school next year. He’s planning to run the marathon again in November 2016, cutting an hour off his time.

“I’d say running has saved my life,” Gonzalez says. “I found hope. Things are brighter than ever.”