1
general::
Long experience of someone or something can make one so aware of the faults as to be scornful. For example, Ten years at the same job and now he hates it? familiarity breeds contempt. The idea is much older, but the first recorded use of this expression was in Chaucer's Tale of Melibee (c. 1386).
American Heritage Idioms
2
general::
Phrase(s): Familiarity breeds contempt.
Prov. People do not respect someone they know well enough to know his or her faults. • The movie star doesn’t let anyone get to know him, because he knows that familiarity breeds contempt.
McGrawhill's American Idioms And Phrasal Verbs