It's overcoming the physical challenges of running that make it so rewarding. I have been running road races for about seven years now. And no matter how many I run, I have yet to run one where I don't think about stopping, dropping out, or walking at least once. I would have thought that it would eventually start to get easier. That running races would become this kind of routine event, and that once I had experienced the physical discomfort of pushing my body and muscles to the limit, it wouldn't really faze me too much anymore. Wrong. It fazes me. A lot. It's part of the internal discussion I have with myself during each race, challenging myself to make it to the next water stop or mile marker. But when I do persevere and I make it through the whole race, pushing through the pain and even allowing myself to experience it to some degree, the feeling of accomplishment at the end is all that much more intense.