Neurosis is the result of a conflict between the ego and its id, whereas psychosis is the analogous outcome of a similar disturbance in the relation between the ego and the external world.
Sigmund FreudOur knowledge of the historical worth of certain religious doctrines increases our respect for them, but does not invalidate our proposal that they should cease to be put forward as the reasons for the precepts of civilization. On the contrary! Those historical residues have helped us to view religious teachings, as it were, as neurotic relics, and we may now argue that the time has probably come, as it does in an analytic treatment, for replacing the effects of repression by the results of the rational operation of the intellect.
Sigmund FreudThe 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.
Sigmund Freud