"I got hit by a 40 pound IED in Afghanistan... it took both of my legs and my left arm," Nicholson explained.
July 6 will forever be Nicholson's "Alive Day." It's a bittersweet time for reflection.
"Summertime is generally a little rougher because that was the time we were deployed over in Afghanistan and we lost a guy and a lot of guys got hit," he said.
And in those first few years following:
"A lot of drinking, a lot of going out and anger and depression," Nicholson recalled.
But then Nicholson met his wife, who he says convinced him to go back to the gym.
Now, he dives into any sport he can.
"I'll try anything once. I'll give it a shot....you just adapt to it. You find out what you can do," Nicholson said.
Nicholson can do a lot. He's gearing up for the swimming and wheelchair basketball competitions at the DoD Warrior Games.
And he already won three gold medals and a silver in track events.
As a father of two, Nicholson wants to set an example for his children. But he also has a message for fellow veterans trying to find their way: work up a sweat, get active.
"You'll find out that you're going to be a lot happier in life," Nicholson said.
He is reminding everyone on his alive day to truly live.
To see a list of the DoD Warrior Games, take a look at their schedule.
For more information about the 2017 DoD Warrior Games, visit their website.
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