Bitter pills may have wholesome effect.

People look for all the mysteries in the sieve of criticism (Swinburne)

Criticism is a kind of wealth and happiness. You might as well collect more, but you can't give them away easily. Just like a festive person, you'd better not give him a clock.

Criticism is the best gift for the noble. Don't give it to a mean person, or you will become a victim of criticism. Well-meaning criticism may not be directed at you, but you must keep it in mind.