Life is often compared to a marathon, but I think it is more like being a sprinter; long stretches of hard work punctuated by brief moments in which we are given the opportunity to perform at our best.
The mind is absolutely instrumental in achieving results, even for athletes. Sports psychology is a very small part, but it's extremely important when you're winning and losing races by hundredths and even thousandths of a second.
Rivalries don't necessarily mean races being close at major championships. I had a rivalry with Butch Reynolds for many years. I won all the races, but Butch was the world record holder before I came into the sport, he was extremely talented and he was the only other man running 43 seconds.