The mind ought to be brought up for examination daily. It was the custom of Sextius when the day was over, and he had retired to his nightly rest, to put these questions to his soul: "What bad habit have you cured today? What vice have you checked? In what respect are you better?" Men will leave off doing wrong if they begin to be ashamed of having done so. Indeed there can be nothing more useful than this practice of thoroughly sifting one's own conduct. How sweet is the sleep which follows this self-examination! How peaceful, how sound, how undisturbed, when the mind has been either praised or admonished, and that secret censor and critic of itself has made the inquiry into its own habits.
I myself use this privilege, and daily plead my own cause before myself. When the light is taken away and my wife has fallen silent, aware of my habit, I review my entire day, going back over what I have done and said. I conceal nothing from myself, omit nothing.
Two formal moves. First, the three questions, asked in order — cured, checked, improved. Notice that all three look for evidence; none asks "did you feel good." Second, the posture: secret, private, before sleep, with the day reviewed honestly — this is examen, the thorough sifting of one's own conduct. Seneca specifically says nothing is hidden — the practice is worthless if you grant yourself exemptions.
Seneca, De Ira (On Anger) 3.36 · trans. John W. Basore (1928)
Context
The locus classicus of the Stoic evening review. Seneca attributes the practice to Sextius (Quintus Sextius the Elder), a Roman philosopher whose late-1st-century-BCE school drew on Pythagorean, Stoic, and Cynic strands. The three questions are the original form; everything since is variation.