It is dangerous for a man too suddenly, or too easily, to believe himself. Wherefore let us examine, watch, observe, and inspect our own hearts; for we are ourselves our own greatest flatterers: we should every night call ourselves to account, “What infirmity have I mastered to-day? what passion opposed? what temptation resisted? what virtue acquired?” Our vices will abate of themselves, if they be brought every day to the shrift.
Seneca the Younger (c. 4 BC-AD 65) Roman statesman, philosopher, playwright [Lucius Annaeus Seneca]
Moral Essays, “On the Happy Life” [De Vita Beata]” [tr. L’Estrange (1834)]
(Source)
Sometimes incorrectly quoted as "Our vices will abort of themselves ...."