From Oliver Wendell Holmes, Sr. (1809–1894), American physician, author, poet, and polymath:
Don’t flatter yourself that friendship authorizes you to say disagreeable things to your intimates. 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 things from his enemies; they are ready enough to tell them.