From Ruiz’s “The Four Agreements“:

Whatever happens around you, don’t take it personally…. If I see you on the street and I say, “Hey, you are so stupid,” without knowing you, it’s not about you; it’s about me. If you take it personally, then perhaps you believe you are stupid. Maybe you think to yourself, “How does he know? Is he clairvoyant, or can everybody see how stupid I am?”

You take it personally because you agree with whatever was said. As soon as you agree, the poison goes through you, and you are trapped in the dream of hell. What causes you to be trapped is what we call “personal importance.” Personal importance, or taking things personally, is the maximum expression of selfishness because we make the assumption that everything is about “me.”

Nothing other people do is because of you. It is because of themselves. All people live in their own dream, in their own mind; they are in a completely different world from the one we live in. When we take something personally, we make the assumption that they know what is in our world, and we try to impose our world on their world.