I don't know if I'm so much fueled by trying to one-up myself so much as passionate about coming up with new and greater challenges. I don't see it as a contest, but as a natural progression.
Beyond racing, I just love the art form of running, of conceiving new ideas like the 50 Marathons in 50 States in 50 Days. It's the ultimate expression of what I love to do, which is run, and travel, and see this great country.