Familiarity breeds contempt, while rarity wins admiration.

[Parit enim conversatio contemptum; raritas conciliat admirationem.]

Apuleius (c. 124 - c. 170 AD) Numidian writer, philosopher, rhetorician [Lucius Apuleius Madaurensis]

On the God of Socrates [De Deo Socratis], ch. 4 [tr. Bohn’s (1853)]

Discussing why the gods do not mingle with humanity. Alt. trans.:

• "Familiarity produces contempt, but infrequency conciliates admiration." [tr. Taylor (1822)]
• "Familiarity breeds contempt, but privacy gains admiration." [Source]
• "Familiarity breeds contempt, but concealment excites interest."

The first part of the phrase is also used as the moral in the traditional English translation of Aesop's "The Fox and the Lion."