About this passageThe Enchiridion is a handbook — the word means something carried in the hand — compiled by Arrian from the lectures of Epictetus, who had been enslaved and later taught philosophy in Nicopolis. This chapter states the school's central claim about disturbance: that the judgement a person forms about an event is a separate thing from the event, and is the part that does the wounding. The closing lines describe three stages of a student's progress by who they blame.
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.
In plainer words
People are not upset by what happens, but by their opinion about what happens. Death, for instance, is not terrible in itself — if it were, Socrates would have thought so too. The terror is in what we think about death. So when we are blocked, upset or grieving, the thing to blame is not other people but our own view of it. Blaming others is what someone does before they have learned anything. Blaming yourself is what someone does while they are learning. Blaming nobody is what it looks like when you have.
A restatement in modern English, written for this collection. The passage above is the text; this is one way of putting it.