The unconscious mind works by associative rather than analytic logic; it constructs links between things and events that are spatially or temporally close. The more often two things coincide or appear in proximity (one right next to or one right after the other), the stronger the link between them generally becomes. However, as will become important to a later discussion of punishment, there are circumstances that can exaggerate the strength of a link even if it is made only once.
The unconscious mind has stronger ties to the past than to the future, but its first allegiance is to the present. It's very difficult to fob it off with promises, no matter how sincere. "I will gladly pay you Tuesday for a little self-control today" tends not to be persuasive when there's a juicy hamburger (or whatever floats your Pavlovian boat) sitting there under your nose. If, however, you have managed to make self-control itself intrinsically rewarding -- if you have associated it often enough and in a variety of circumstances with strong and immediate payoffs -- you have some leverage. There are marker-trained dogs who will fetch whole hot dogs and deliver them unmolested to their owners' hands... in return for a 1/4-inch cube of hot dog. This takes some work.
Image by Marc Greisinger.