The ego operates according to the "reality" principle...
In Freudian psychological terms, the reality principle is the capacity of the psyche to evaluate the truth of the outer world, and to follow up on it as needs be, rather than following up on the pleasure principle. Enabling the person to concede instant delight, the reality principle is the administering standard of the moves made by the ego, after its moderate advancement from a "pleasure ego" into a "reality ego ".