For mostly historical reasons, we should include the Psychodynamic perspective. In this model, personality comes from the interaction of three basic psychic structures, the id, ego, and superego.

Freud's theory came at a time when it was fashionable to apply the concepts of thermodynamics to pretty much everything. The id, ego, and superego have to share a finite amount of psychic "energy", and growth and development is a matter of approaching some kind of thermal equilibrium.

The whole idea seems pretty hokey nowadays, but I'm sure it seemed like a good idea at the time.