" The development of inner skills is required, but it is interesting to note that if, while learning tennis, you begin to learn how to focus your attention and how to trust in yourself, you have learned something far more valuable than how to hit a forceful backhand. The backhand can be used to advantage only on a tennis court, but the skill of mastering the art of effortless concentration is invaluable in whatever you set your mind to. "

― W. Timothy Gallwey , The Inner Game of Tennis: The Classic Guide to the Mental Side of Peak Performance