§6.19.1Μή, εἴ τι αὐτῷ σοὶ δυσκαταπόνητον, τοῦτο ἀνθρώπῳ ἀδύνατον ὑπολαμβάνειν, ἀλλ’ εἴ τι ἀνθρώπῳ δυνατὸν καὶ οἰκεῖον, τοῦτο καὶ σεαυτῷ ἐφικτὸν νόμιζε.
Do not, if something is difficult for you yourself to accomplish, assume that this is impossible for a human being; but if anything is possible and proper for a human being, consider this to be attainable by yourself as well.