Definition: The central concept of stoicism, that certain things are under your control, while others are not.
Reference: Epictetus, Enchiridion, 1: "Of all existing things some are in our power, and others are not in our power. In our power are thought, impulse, will to get and will to avoid, and, in a word, everything which is our own doing. Things not in our power include the body, property, reputation, office, and, in a word, everything which is not our own doing."
Reference: Serenity prayer, adopted by 12-step programs: "God, grant me the serenity to accept the things I cannot change, Courage to change the things I can, And wisdom to know the difference."
Example: Insults: (1) someone has to say something that is meant to offend (2) you have to take this as offensive (3) you have to react to the insult, as without reaction the insult falls flat.
Insight: We cannot guarantee how most things will turn out.
Principle: Focus energy and resources on affected what you can control, and not on what you cannot.
