Despite all of that, he never noticed feelings of PTSD that befall so many veterans because he distracted himself with athletic achievements – beating guys with both their legs in golf, biking up mountains and summiting Mt. Kilimanjaro – until he found himself recovering alone at home from one of his final surgeries.
"I couldn't do anything. I couldn't keep up with my then 3-year-old daughter, couldn't play golf, and those thoughts that I used to be able to chase away with a golf club or my road bike just kept coming back," Nevins, 43, tells PEOPLE.
"I had learned the statistics about suicide, like that 400,000 soliders live with PTSD. But I had never identified with that group because I never had PTSD. I never delt with that. The one statistic I never understood was the 22 veterans a day that take their own life."
Nevins didn't want to worry his veteran friends and coworkers at the Wounded Warrior Project, so instead he called up a friend who suggested something Nevins had never even considered trying.
"She said the stupidest thing anyone's ever said to me," Nevins recalls, laughing. "She said 'You need some yoga in your life.' And I said absolutely not."
The muscular guy who joined the Army right out of high school didn't want to consider it.
"I'm not a mother earth guy. I eat meat, I own guns," Nevins says.
But with some convincing, he agreed to try meditation. Once he got the hang of it, he stopped being controlled by his negative thoughts, and Nevins' friend got him to agree to three private yoga classes.
RELATED VIDEO: Men at Work! Prince William Tells Prince Harry, 'Game On,' as They Wear Hard Hats to Build Homes for Veterans
"This was a tough moment for me because no one ever saw me with my legs off," Nevins says. "But I got on that mat and got in warrior pose. I started to lift up my arms up for this pose and got this burst of energy like lightning. I had this moment with the universe. It was like the earth was saying, 'Dan, where have you been for the last 10 years?' It was incredible."
Right after, Nevins went on a yoga retreat to become a teacher, and for the first time, he had to take off his legs in a room full of people.
"I hit a wall. I felt like I couldn't move, I was pouring with sweat," Nevins says. "I think I was having a panic attack. I was distracted the whole time, thinking I was ruining the class for everyone."
But once the class ended, everyone ran up to tell him that he was inspiring.
"That's when I realized that it was all in my head, that shame and that feeling of 'I don't belong here,' " Nevins says.
"For me to take off my legs, it's about four seconds. Not even an issue. But taking them off at that moment was the hardest thing I've ever done in my life. I realized that everybody has their 'legs' to take off, whatever it is to them."
Nevins is now a certified yoga instructor and motivational speaker, teaching across the globe and even at the White House. He tries to reach as many veterans as possible through yoga.
The #Eastereggroll has been Amazing!! Meeting and practicing with, learning from and teaching to the most amazing human beings... Including this gem, the insanely talented @bibimcgill, has been a huge blessing for me today. I'll certainly cherish every moment from the #yogagarden, I hope this continues to the next administration!! #letscelebrate #woundedwarriorproject #whybaptisteyoga
"Everyone is fighting some war. Everyone has those scars that they carry around," Nevins says. "It doesn't have to be from explosions or war. And I know that almost all of my students know a veteran, so I tell them to invite them to yoga. Because it might just save their life."
"I've never been happier," he continues. "I'm doing exactly what I'm supposed to be doing. It's weird to be thinking like that because I realized that means that I was actually supposed to lose my legs – and I actually believe that."