When you think that you are beautiful, you are liable to think that you are more beautiful than others, and such a thought is not a beautiful thought. To recognize or criticise ugliness and inferiority in others is to create the inferior and the ugly in yourself, and what you create in yourself will sooner or later be expressed through your mind and personality.

Chapter 7, p. 115–116 - Your Forces and How to Use Them (1912)