“I tend to imagine the self-regulating system like little gremlins hoping on the pain side of the balance to counteract the weight on the pleasure side. The gremlins represent the work of homeostasis, the tendency of any living system to maintain physiologic equilibrium. Once the balance is level, it keeps going, tipping an equal and opposite amount to the side of pain.
In the 1970s social scientists Richard Solomon and John Corbett called this reciprocal relationship between pleasure and pain "The Opponent Process Theory". Any prolonged or repeated departure from hedonic or adaptive neutrality has a cost. That cost is an after-reaction, that is opposite in value to the stimulus, or as the old saying goes: "What goes up, must come down".”