Derek Ibbotson disliked sprinting, and consequently he was outsprinted in many races. He decided to spend a winter with his club's sprint group in addition to his normal cross-country training. He became one of the fastest finishers ever in mile races. He also broke the mile record. We don't hear much about will-power training in sport.
Athletes have to resist certain excessive social behaviour patterns which are accepted as the norm.
This is defensive use of the will. We can - and in doing so improve our performance. A middle-aged female took up running for the marathon. She had not participated in sport of any kind for 25 years. She was told to run for one minute and each successive day to add a minute.