On June 30, Carey Hart made it official: “The fat lady sang,” he tweeted. “Thank you so much everyone. The fans, my sponsors, the industry and my family. Feel like I went out good!!! Now I drink.”

It wasn’t just the end of his run at the 2012 X Games in LA, where Hart placed seventh in Moto X Speed & Style. In 140 characters, Hart was saying goodbye to a professional motocross career that started in the Vegas desert and spanned three decades, helping to put his sport on the map. At age 37, he was retiring.

Hart and motocross grew up together. Born in California, Hart moved to Las Vegas young and started racing at 6. By 12, he was eying sponsorships and bigger competitions, thinking he might be able to make a living with this whole motorcycle thing, rather than working construction for his dad. At the same time, motocross itself was evolving, from “good old boy back-alley sport” to prime-time attraction with ESPN highlights, stadium tours and X Games competitions.

But the corporate dollars and TV cameras don’t make the sport any less brutal. Motocross can chew up even the toughest competitors if they ride too long or make a slight miscalculation. In other words, you have to know when it’s time to go.

“There’s always part of you that’s like, I can keep going,” says Hart, who battled back injuries going into this summer’s X Games. “Mentally, I’m probably always going to be 15, but age-wise I’m 37, and physically I’m probably closer to 67.”

In 2003, motocross almost spit Hart out. He was riding in Tony Hawk’s Boom Boom HuckJam tour, a choreographed show that blended skate, BMX and motocross into a ballet of wheels and agility. “We would actually jump over the top of the vert ramp, so just timing and knowing the routine was critical,” Hart explains of the motocross segment. But one night the timing was off: “As I came into my approach on the takeoff, one of the skaters popped out on the deck right in front of me. So I had to make the split second decision to either go right into the crowd or left into the vert ramp. … I basically jumped 75 feet into a brick wall.”

Hart broke both legs and both arms and had blood clotting so severe it almost killed him. Doctors told him he’d be lucky to walk normally again, but three years later, he did them one better: He got back on his bike.

“It was one of the better highs of my whole career,” Hart says of that first ride during his recovery. “And at that point it was a leisure thing. I had already come to grips with the fact that I was going to have to retire and I couldn’t pursue it as a career anymore.”

But retirement didn’t stick. Hart kept riding—through injuries, aging and tragedy. In 2008, Hart’s younger brother Anthony died after crashing during a motocross practice session in Connecticut. Still, Hart couldn’t give it up. “People might think I’m crazy, but it’s literally like in your blood. … It’s just not a trade or a hobby; it’s just part of you.”

Which is why it’s taken so long for him to look retirement in the eye again. Today, Hart’s spending more time on expanding Hart & Huntington Tattoo Company, which has a location at the Hard Rock Hotel in Las Vegas, and he’s in the midst of revamping the supercross team that’s become his passion project. Come January, he’ll hit the road in a tour bus with wife Pink and their 1-year-old daughter Willow for Pink’s 14-month concert tour.

But even as he talks about motocross as a “young man’s sport” and says that fatherhood has made him reconsider the “real stupid stuff” he used to do, Hart is on his way to test a vehicle for his next truck race. He’s giving up the competition mindset that makes people push their limits and sometimes charge right past them, but he’ll never park his motorcycle. It’s in his blood—just part of him.