Men are disturbed not by the things which happen, but by the opinions about the things…
THE ENCHEIRIDION, OR MANUAL.
Men are disturbed not by the things which happen, but by the opinions about the things; for example, death is nothing terrible, for if it were it would have seemed so to Socrates; for the opinion about death that it is terrible, is the terrible thing. When then we are impeded, or disturbed, or grieved, let us never blame others, but ourselves—that is, our opinions. It is the act of an ill-instructed man to blame others for his own bad condition; it is the act of one who has begun to be instructed, to lay the blame on himself; and of one whose instruction is completed, neither to blame another, nor himself.