Many of us have little tricks we play on ourselves to make us do the things we ought to do or to keep us from the things we ought to foreswear. Sometimes we put things out of reach for the moment of temptation, sometimes we promise ourselves small rewards, and sometimes we surrender authority to a trustworthy friend who will police our calories or our cigarettes. We place the alarm clock across the room so we cannot turn it off without getting out of bed. People who are chronically late set their watches a few minutes ahead to deceive themselves. I have heard of a corporate dining room in which lunch orders are placed by telephone at 9:30 or 10:00 in the morning; no food or liquor is then served to anyone except what was ordered at that time, not long after breakfast, when food was least tempting and resolve was at its highest. A grimmer example of a decision that can’t be rescinded is the people who have had their jaws wired shut. Less drastically, some smokers carry no cigarettes of their own, so they pay the “higher” price of bumming free cigarettes.

In these examples, everybody behaves like two people, one who wants clean lungs and long life and another who adores tobacco, or one who wants a lean body and another who wants dessert. The two are in a continual contest for control: the “straight” one often in command most of the time, but the wayward one needing only to get occasional control to spoil the other’s best laid plan.

Thomas Schelling, ‘Egonomics, or the Art of Self-Management’, The American Economic Review, vol. 68, no. 2 (May, 1978), p. 290