We play because we have an exuberance of spirits and energy, but we are also exuberant because we play. We seek to play not only because it is part of our evolutionary history, but because we know that more often than not it will bring pleasure . . . Play is a vital facilitator, shaper, and motivator: it allows the pleasurable practice of improbable twists and turns in instinctive behaviors which, in turn, creates for the animal a wider range of possibilities for future actions.

Kay Redfield Jamison, Exuberance