PLEASURE-PRINCIPLE AND REALITY-PRINCIPLE : Respectively, the desire for immediate gratification vs. the deferral of that gratification. Quite simply, the pleasure-principle drives one to seek pleasure and to avoid pain. However, as one grows up, 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" (Introductory Lectures 16.357).