Sigmund Freud Quote
The functional importance of the ego is manifested in the fact that normally control over the approaches to motility devolves upon it. Thus in its relation to the id it is like a man on horse back, who has to hold in check the superior strength of the horse; with this difference, that the rider tries to do so with his own strength while the ego uses borrowed forces.
The Standard Edition of the Complete Psychological Works of Sigmund Freud (ed. 1961)