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Criticism is futile because it puts a person on the defensive and usually makes them strive to justify themselves. Criticism is dangerous, because it wounds a person's precious pride, hurts their sense of importance, and arouses resentment.

Dale Carnegie (0101). “Best of Dale Carnegie Vol-I”, p.13, Prabhat Prakashan
Criticism is futile because it puts a person on the defensive and usually makes them strive to justify themselves. Criticism is dangerous, because it wounds a person's precious pride, hurts their sense of importance,