Narcissism of small differences
The Narcissism of small differences is a term coined by Sigmund Freud in 1917, based on the earlier work of British anthropologist Ernest Crawley. The term describes the manner in which our negative feelings are sometimes directed at people who resemble us, while we take pride from the "small differences" that distinguish us from them.
The term appeared in Civilization and Its Discontents (1929-1930) in relation to the application of the inborn aggression in man in ethnic conflict.
Glen O. Gabbard, M.D. suggested Freud's "Narcissism of Small Difference" provides a framework within which to understand that in a loving relationship there can be a need to find, and even exaggerate, differences in order to preserve as feeling of separateness and self.