Young persons have usually a cheerful and satirical turn, untempered by seriousness, thus often making themselves disagreeable.
No part is easier to play than that of being always pleasant; and the applause we sometimes receive in censuring others is not worth being exposed to the chance of offending them when they are out of temper.
 François de La Rochefoucauld, Reflections; or Sentences and Moral Maxims (1665). copy citation

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Author François de La Rochefoucauld
Source Reflections; or Sentences and Moral Maxims
Topic seriousness temper
Date 1665
Language English
Reference
Note Translated by J. W. Willis Bund
Weblink http://www.gutenberg.org/files/9105/9105-h/9105-h.htm

Context

“There are others again whose cleverness is limited to their own business, and who know how to turn everything to their own advantage. It is possible to have a serious turn of mind, and yet to talk pleasantly and cheerfully. This class of mind is suited to all persons in all times of life. Young persons have usually a cheerful and satirical turn, untempered by seriousness, thus often making themselves disagreeable. No part is easier to play than that of being always pleasant; and the applause we sometimes receive in censuring others is not worth being exposed to the chance of offending them when they are out of temper. Satire is at once the most agreeable and most dangerous of mental qualities. It always pleases when it is refined, but we always fear those who use it too much, yet satire should be allowed when unmixed with spite, and when the person satirised can join in the satire.” source