Familiarity breeds contempt

The better you know someone or something, the more likely you are to find faults and lose respect for them.

This saying comes from Aesop's fable 'The Fox and the Lion,' where a fox becomes less afraid of a lion after repeated encounters. The Latin version 'nimia familiaritas parit contemptum' was well-known in medieval times, and the English phrase has been used since at least the 14th century.