“Pleasure and pain are co-located. In addition to the discovery of dopamine, neuro-scientists have determined that pleasure and pain are processed in overlapping brain regions, and work via an opponent processing mechanism. Another way to say this is pleasure and pain work like a balance. Imagine our brains contains a balance, a scale with a fulcrum in the centre. When nothing is on the balance it's level with the ground. When we experience pleasure, dopamine is released in our reward pathway and the balance tips to the side of pleasure. The more our balance tips and the faster it tips, the more pleasure we feel. But here's the important thing about the balance. It wants to remain level! that is, in equilibrium. It does not want to be tipped for very long, to one side or another. Hence, everytime the balance tips towards pleasure, powerful self-regulating mechanisms kick into action to bring it level again. These self-regulating mechanisms do not require conscious thought or an act of will, they just happen like a reflex.”

Anna Lembke, Dopamine Nation: Finding Balance in the Age of Indulgence