Criticism is futile

Criticism is futile because it puts a person on the defensive and usually makes him strive to justify himself. Criticism is dangerous, because it wounds a person’s precious pride, hurts his sense of importance, and arouses resentment.

~ Dale Carnegie, How to Win Friends & Influence People

Never criticize

There is nothing else that so kills the ambitions of a person as criticisms from superiors. I never criticize anyone. I believe in giving a person incentive to work. So I am anxious to praise but loath to find fault. If I like anything, I am hearty in my approbation and lavish in my praise.

~ Charles Schwab