What is the pleasure principle in psych?

The Force: Essentially, this is a psychoanalytic term for the tendency or drive to achieve pleasure and avoid pain as the chief motivating force in behavior.

Primitive: Freud described maturation as a process whereby immediate pleasure (and/or avoidance of pain) gave way to the will to defer temporarily pleasure (or tolerate pain) by keeping in mind the superior rewards to be had by doing so. This capacity requires a growing understanding of reality i the teeth of one's wishful fantasies.