familiarity breeds contempt

Overexposure to or knowing something or someone too thoroughly can turn liking into hostility. The idea behind this expression dates from ancient times—the Roman writer Publilius Syrus used it about 43 B.C.—and approximately twelve hundred years later Pope Innocent III repeated it, also in Latin. The first record of it in English appeared in Nicholas Udall’s translation of Erasmus’s sayings (1548): “Familiaritye bringeth contempt.” Later writers often stated it with humor or irony, notably Mark Twain in his unpublished diaries (Notebooks, c. 1900): “Familiarity breeds contempt—and children.”