I once read a story in a golf book about the power of the mind. It told of a man who was a POW in Viet Nam for over 7 years. To keep his sanity he would do mind exercises every day. One of the things he did was visualize playing golf at his home course. Each day he would begin his mental round by driving to the course, paying his green fees, step up to the first tee and walk 18 holes.
He envisioned every step, every practice swing, every shot, and every outcome. Every "round" would take him about four hours. During these rounds he was locked in a small cage, barely large enough to stand it.
After he was released, he went home and took the first opportunity to play a round of golf. He shot a 75, the best round of his life.
Anyone who has read about meditation or has done it themselves knows it can elevate your physical performance, as well as other things. Mental preparation is known to improve your performance in any endeavor just as "stinkin' thinkin' will hurt you.
And then there's the story of a sailor on a Navy ship. A 500 pound bomb had landed on the deck but didn't explode. His crewmates said he ran over to it and lifted it and dumped it in the ocean. He said he didn't remember much, just that he was scared to death the thing would explode and they would all die. He did say, however, that he was sore as hell later on. And no, he wasn't a weightlifter or a circus strongman. He was said to be an average-sized guy.
When the mind is singularly focused, we can do amazing things.