Uncertainty often makes us hesitant, but when used as motivation, it can produce the most outstanding results. The most successful people I've come across have mental discipline, they harness uncertainty and embrace the possibility of failure. As Mike has shown, a lifetime of success far outweighs temporary discomfort.
Long distance runners are a bizarre group of people to those who find comfort in stillness, pleasure in overindulgence, and reassurance in conformity. I know this because I was not always a runner. There was a time that I scoffed at runners and the strange counterculture of running. But, now I know better.