This is the main thing you should practice. Every morning when you go out, look at every person you see and hear. Ask yourself: What did you just witness? A beautiful man or woman? Apply the rule. Is this something you control or not? You don't control it. Dismiss it. What did you see? A man crying over his dead child? Apply the rule. Death is not something you control. Dismiss it. Did you meet a government official? Apply the rule. What is a government position? Do you control it or not? You don't control it. Dismiss this too. It doesn't pass the test. Throw it out. It's nothing to you.
Against (or with respect to) this kind of thing chiefly a man should exercise himself. As soon as you go out in the morning, examine every man whom you see, every man whom you hear; answer as to a question, What have you seen? A handsome man or woman? Apply the rule. Is this independent of the will, or dependent? Independent. Take it away. What have you seen? A man lamenting over the death of a child. Apply the rule. Death is a thing independent of the will. Take it away. Has the proconsul met you? Apply the rule. What kind of a thing is a proconsul's office? Independent of the will or dependent on it? Independent. Take this away also; it does not stand examination; cast it away; it is nothing to you.