Freud's Id, Ego & Superego.

The id comprises the unorganised part of the personality structure that contains the basic drives. The id acts according to the "pleasure principle", seeking to avoid pain or unpleasure aroused by increases in instinctual tension.

The Ego acts according to the reality principle; i.e. it seeks to please the id’s drive in realistic ways that will benefit in the long term rather than bringing grief.

Regression, according to psychoanalyst Sigmund Freud, is a defense mechanism leading to the temporary or long-term reversion of the ego to an earlier stage of development rather than handling unacceptable impulses in a more adult way.