How much of your time is spent thinking about what that rude person said to you? Or whether so-and-so will like you. Or if your coworker will follow through on their part of the assignment? And not just time. How much anguish, angst, and anxiety has it caused you? How much sleep have you lost because of these things outside of your control?

Marcus Aurelius—someone who, as Emperor, had his share of critics and frustrating subordinates—said, “Tranquility…comes when you stop caring what they say. Or think, or do. Only what you do.”

How they feel isn’t in your control. What they do (or don’t do) isn’t in your control. What they think of you isn’t. You know what is? What you do. The actions you take. The actions you take in response to the actions they take (or don’t take). Focus on the part that’s in your control, stress only about what you do, and you’ll find the tranquility Aurelius was talking about.