Seneca · On a promising pupil
Letters 34.4
I see such a person in you, if only you go steadily on and bend to your task, and see to it that all your actions and words harmonize and correspond with each other and are stamped in the same mould. If a man’s acts are out of harmony, his soul is crooked. Farewell.
Seneca, Letters to Lucilius 34.4, translated by Richard Mott Gummere