The paradox of hedonism, also called the pleasure paradox, is the idea in the study of ethics which points out that pleasure and happiness are strange phenomena that do not obey normal principles. The paradox of hedonism points out that pleasure cannot be acquired directly, it can only be acquired indirectly.

Happiness is often imprecisely equated with pleasure. If, for whatever reason, one does equate happiness with pleasure, then the paradox of hedonism arises. When one aims solely towards pleasure itself, one's aim is frustrated.

Suppose John likes to collect stamps. According to most models of behavior - most economic, psychological and social conceptions of behavior, it is believed that John likes collecting stamps because he gets pleasure from collecting stamps. Stamp collecting is an avenue towards acquiring pleasure. However, if you tell John this, he will likely disagree. He does get pleasure from collecting stamps, but this is not the process that explains why he collects stamps. It is not as though he says, “I must collect stamps so I can obtain pleasure”. Collecting stamps is not just a means toward pleasure. He just likes collecting stamps.
This paradox is often spun around backwards, to illustrate that pleasure and happiness cannot be reverse-engineered. If for example you heard that collecting stamps was very pleasurable, and began a stamp collection as a means towards this happiness, it would inevitably be in vain. To achieve happiness, you must not seek happiness directly, you must strangely motivate yourself towards things unrelated to happiness, like the collection of stamps.

The hedonistic paradox would probably mean that if one sets the goal to please oneself too highly then the mechanism would in fact jam itself.