Exercise and sports are greatly affected by what goes into the mind, and the mind is greatly affected by sports and exercise as well. This is true among exercisers at all levels, despite their different goals. A major element in mental training is visualization ... Visualizing a positive outcome can create a pattern of success, as long as you set realistic and specific goals.
Grete Waitz, Gloria Averbuch (2000). “On The Run: Exercise and Fitness for Busy People”, Rodale Books