Seneca · On practising what you preach
Letters 20.1
If you are in good health and if you think yourself worthy of becoming at last your own master, I am glad. For the credit will be mine, if I can drag you from the floods in which you are being buffeted without hope of emerging. This, however, my dear Lucilius, I ask and beg of you, on your part, that you let wisdom sink into your soul, and test your progress, not by mere speech or writings, but by stoutness of heart and decrease of desire. Prove your words by your deeds.
Seneca, Letters to Lucilius 20.1, translated by Richard Mott Gummere