“You will become way less concerned with what other people think of you when you realise how seldom they do.”
I adore David Foster Wallace. This comes from a chapter in Infinite Jest where he lists the things things you will learn if "by the virtue of charity or the circumstance of desperation" you come to spend time at a substance-recovery facility.
I take it as a massive comfort that most people are not actually thinking about you at all, that they are probably just worrying about what you think of them.