According to freud's psychoanalytic theory, the ego abides by the principle.

The ego abides by the reality principle. Sigmund Freud developed a theory of psychic consciousness, the postulate that we are governed by 3 psychic entities that are antagonistic between them and create a conflict, the result of that conflict is what defines our behavior. The ego is the second psychic instance, it is the entity of which we are aware and we consider our own identity, it serves as an intermediary between the other two entities, the Id and the Superego.

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