Good-breeding never forgets that amour-propre is universal.
 Oliver Wendell Holmes Sr., The Autocrat of the Breakfast-Table (1858). copy citation

Context

“On the contrary, the nearer you come into relation with a person, the more necessary do tact and courtesy become. Except in cases of necessity, which are rare, leave your friend to learn unpleasant truths from his enemies; they are ready enough to tell them. Good-breeding never forgets that amour-propre is universal. When you read the story of the Archbishop and Gil Blas, you may laugh, if you will, at the poor old man’s delusion; but don’t forget that the youth was the greater fool of the two, and that his master served such a booby rightly in turning him out of doors.” source