From the very beginning, make it your practice to say every harsh impression, "you are an impression and not at all what you appear to be." Next, examine and test it by the rules you possess, the first and greatest of which is this- whether it belongs to the things in our control or not in our control, and if the latter, be prepared to respond, "It is nothing to me."

—Epictetus, Enchiridion, 1.5(resource) The Daily Stoic: 366 Meditations on Wisdom