Snippets from the Handbook 4

Make it your study then to confront every harsh impression with the words, "You are but an impression, and not at all what you seem to be." 

Then test it by those rules that you possess; and first by this—the chief test of all—"Is it concerned with what is in our power or with what is not in our power?" 

And if it is concerned with what is not in our power, be ready with the answer that it is nothing to you. 

—Epictetus, The Handbook 1