Seneca · On the true joy which comes from philosophy
Letters 23.1
Do you suppose that I shall write you how kindly the winter season has dealt with us,—a short season and a mild one,—or what a nasty spring we are having,—cold weather out of season,—and all the other trivialities which people write when they are at a loss for topics of conversation? No; I shall communicate something which may help both you and myself. And what shall this “something” be, if not an exhortation to soundness of mind? Do you ask what is the foundation of a sound mind? It is, not to find joy in useless things. I said that it was the foundation; it is really the pinnacle.
Seneca, Letters to Lucilius 23.1, translated by Richard Mott Gummere