Pathology has made us acquainted with a great number of states in which the boundary lines between the ego and the external world become uncertain or in which they are actually drawn incorrectly. There are cases in which parts of a person's own body, even portions of his own mental life - his perceptions, thoughts and feelings -, appear alien to him and as not belonging to his ego; there are other cases in which he ascribes to the external world things that clearly originate in his own ego and that ought to be acknowledged by it.
Sigmund FreudThe expectation that every neurotic phenomenon can be cured may, I suspect, be derived from the layman's belief that the neuroses are something quite unnecessary which have no right whatever to exist. Whereas in fact they are severe, constitutionally fixed illnesses, which rarely restrict themselves to only a few attacks but persist as a rule over long periods throughout life.
Sigmund FreudExperience teaches that for most people there is a limit beyond which their constitution cannot comply with the demands of civilization. All who wish to reach a higher standard than their constitution will allow, fall victims to neurosis. It would have been better for them if they could have remained less "perfect".
Sigmund Freud