In 1995, Karnazes ran his first Badwater Ultramarathon, a 135-mile trek that starts in Death Valley, California, in the middle of summer and finishes at the Mt. Whitney Portals, 8,360 feet above sea level. After running 72 miles in 120-degree heat, Karnazes collapsed on the side of the road suffering from hallucinations, diarrhea, and nausea. He had pushed himself to the point of death to find out whether he was strong enough to survive. He was. Though he didn’t finish the race that year, Karnazes came back the next and placed 10th. He won it on his fifth attempt, in 2004. “Somewhere along the line, we seem to have confused comfort with happiness,” he says.