Sourced
Men are disturbed not by the things which happen, but by the opinions about the things.
Source: Enchiridion 5, tr. George Long
Authors / Epictetus
Epictetus wrote nothing himself; his student Arrian recorded the Discourses and the short handbook, the Enchiridion. His core idea — that we are disturbed by our judgments, not by events — still drives modern cognitive therapy.