Meditations
Marcus Aurelius · c. 170-180
The private notebook of a Roman emperor, reminding himself how to live: what is in his control, how to deal with difficult people, how small any one day is. Written for nobody, which is why it still reads as honest.
Worth knowing: Stoicism is a philosophy, not a therapy. The founders of cognitive therapy named it as a forerunner, which is a historical link, not evidence.
How to start: A page a day. The Gregory Hays translation (2002) is the most readable modern English.