Sigmund Freud on Ego

“The ego represents what we call reason and sanity, in contrast to the id which contains the passions.”

“It is easy to see that the ego is that part of the id which has been modified by the direct influence of the external world.”

“One might compare the relation of the ego to the id with that between a rider and his horse. The horse provides the locomotor energy, and the rider has the prerogative of determining the goal and of guiding the movements of his powerful mount towards it. But all too often in the relations between the ego and the id we find a picture of the less ideal situation in which the rider is obliged to guide his horse in the direction in which it itself wants to go.”

“Towards the outside, at any rate, the ego seems to maintain clear and sharp lines of demarcation. There is only one state — admittedly an unusual state, but not one that can be stigmatized as pathological — in which it does not do this. At the height of being in love the boundary between ego and object threatens to melt away. Against all the evidence of his senses, a man who is in love declares that "I" and "you" are one, and is prepared to behave as if it were a fact.”