The following comes from "Mental Toughness: Baseball’s Winning Edge" by Karl Kuehl, John Kuehl, and Casey Tefertiller:
In the bullpen and between innings, Greg Maddux spends most of his time working out of the stretch. The toughest pitches during a game come from the stretch, and Maddux wants to be ready, both physically and mentally. Knowing that he can make his best pitches from the stretch in the bullpen builds a confidence that carries over into the game.
Practice is a time to build confidence.
Consistently doing it right in practice builds confidence that carries over into the game.
Being prepared also means being well conditioned. Added strength and stamina from workouts give an athlete confidence in his physical abilities to meet the challenges of competition.
It may sound almost circular, but confidence breeds success, and success leads to confidence. The trick is to use success to build a level of confidence.
A process of replay and pre-play enhances confidence. A player can replay past successes in his mind, recalling past successes that have led to his current level. The pre-play is the process of visualization, in which an athlete envisions every situation in his mind in order to prepare for what will actually occur on the field. Curt Schilling goes so far as to acquire his own personal computer program that plays his previous outings in order to help him prepare for upcoming games. In visualization, as we shall see, every thought should be positive.
Confidence does not always mean achievement—it means believing in the ability to overcome challenges and adversity. A confident player can fall into a slump and know that he will somehow find his way out rather than folding in despair.