Don't flatter yourselves that friendship authorizes you to say disagreeable things to your intimates. On the contrary, the nearer you come into relation with a person, the more necessary do tact and courtesy become. Oliver Wendell Holmes, Sr.
Telephone, n. An invention of the devil which abrogates some of the advantages of making a disagreeable person keep his distance. Ambrose Bierce
If you have learned how to disagree without being disagreeable, then you have discovered the secrete of getting along - whether it be business, family relations, or life itself. Bernard Meltzer
The excellency of every art is its intensity, capable of making all disagreeable evaporate. John Keats