The Enchiridion, Section 5 — In Plain English

Epictetus — The Slave

It's not things that upset you. It's how you think about them. Death, for example, is not frightening on its own. If it were, Socrates would have been afraid of it. But the terror comes from our belief about death — that it's terrible. So when you feel blocked, disturbed, or sad, don't blame other people. Blame yourself. Actually, blame your own thoughts. Here's how you can tell where someone stands: A beginner blames others for his problems. Someone learning blames himself. Someone who truly gets it blames no one.

Epictetus — The Slave Original

Men are disturbed not by things, but by the views which they take of things. Thus death is nothing terrible, else it would have appeared so to Socrates. But the terror consists in our notion of death, that it is terrible. When, therefore, we are hindered or disturbed, or grieved, let us never impute it to others, but to ourselves—that is, to our own views. It is the action of an uninstructed person to reproach others for his own misfortunes; of one entering upon instruction, to reproach himself; and one perfectly instructed, to reproach neither others nor himself.