Pleasure principle (psychology)

The pleasure principle and the reality principle are two psychoanalytical terms coined by Sigmund Freud.

Respectively, the desire for immediate gratification versus the deferral of that gratification. Quite simply, the pleasure principle drives one to seek pleasure and to avoid pain. However, as one matures, one begins to learn the need sometimes to endure pain and to defer gratification because of the exigencies and obstacles of reality: "An ego thus educated has become reasonable; it no longer lets itself be governed by the pleasure principle, but obeys the reality principle, which also at bottom seeks to obtain pleasure, but pleasure which is assured through taking account of reality, even though it is pleasure postponed and diminished" (Sigmund Freud, Introductory Lectures 16.357).

http://en.wikipedia.org/wiki/Pleasure_principle_%28psychology%29