When American discus thrower Sam Mattis steps on the field for the first time at the 2020 Tokyo Olympics, few viewers will know the journey that brought him to that moment.

The 27-year-old's inclusion on Team USA is the culmination of a five-year grind that saw him scraping by financially and ultimately led him to "reevaluate my relationship with money," he tells CNBC Make It.

Though he graduated from the University of Pennsylvania's Wharton School in 2016 with a degree in economics and had a lucrative job offer at JPMorgan Chase, Mattis says he "always knew that finance wasn't where I wanted to ultimately end up, even if it's where I started."

He had gone to Wharton partially out of a desire to create financial security for himself — his family struggled financially while he was growing up — but he couldn't pass on the chance to pursue something personally fulfilling.

Mattis knew that by turning down Wall Street to train for the Olympics he'd be setting himself up for a financially tight few years, but "I don't think I truly understood the scope of the financial struggle I'd be going through," he says.

Since 2016, Mattis has lived off of between $25,000 and $35,000 a year, with sources of income ranging from unemployment to tutoring to doing marketing for a local pharmacist. To stretch his income, he's been living in "beat-up apartments," driving "old used cars" and buying groceries at a nearby farmers market because it was cheaper than going to the supermarket.

"There were a bunch of times when I'd be just barely getting by at the end of the month between rent and car payments and everything like that," he says. "I was doing whatever I could to make a little extra money."

Despite this, Mattis says that he was one of the more fortunate athletes in the tight-knit community he trained with. Because he's one of the best discus throwers in the country, he receives a $12,000 annual stipend from USA Track and Field.

"Most of those other guys who are just coming on the scene or maybe they're 4th in the country instead of 3rd, they're also working full-time jobs [in addition to training]," he explains. Mattis says that the ability to work part-time instead of full-time can make a big difference.

The balance between financial hardship and athletic performance creates what he calls a "virtious and vicious" cycle, where top performers are rewarded with sponsorships and stipends and can spend more time focused on training, while athletes who might have a bad showing at a meet lose out on financial opportunities and are forced to work more, which prevents them from concentrating on their sport.

"What most of us do with athletics, whether it's the lifting, the throwing, the technique work and the recovery afterwards, that's already a full-time job," Mattis says. "And it's a physically and mentally exhausting job. To add five to eight hours of work on top of that every day makes it almost impossible."

"There's barely enough sponsor demand for the best athletes in [discus]," he adds. "If you're not a national champion and going to compete at some international meets, you're not getting anything in this sport."

By earning a spot on Team USA, Mattis will receive a $10,000 bonus, as well as a $6,000 prize for his third place finish at the Olympic Trials. The money, he says, will go a long way toward helping him continue his training after Tokyo. He plans to focus on trying to make the 2024 Olympic team as well.

But once he officially hangs up his spikes, don't expect Mattis to make a return to the world of finance. He says that five years of "having no money" have made him reassess what is important to him. Now, he has an eye on the field of environmental justice once his athletic career is over.

"I learned to appreciate the people around me a lot more and take pride in and try and get some happiness out of what I was doing," Mattis says. "I reoriented myself in a direction where even if I continued to not have money for the rest of my life, I'll still feel fulfilled and happier than if I did have money."

He adds that he has no regrets about the struggles he's endured on his journey to Tokyo.

"I did all this to try to make an Olympic team, and I made one, so that's great," Mattis says. "But even if I didn't make it, I think the journey and all the obstacles I had to go through along the way have been invaluable."

The men's discus throw event is scheduled to take place between July 30 and 31.

Disclosure: CNBC parent NBCUniversal owns NBC Sports and NBC Olympics. NBC Olympics is the U.S. broadcast rights holder to all Summer and Winter Games through 2032.

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