Plato, Laws 732b

ἄλλοις ἃ μὴ ἐπιστάμεθα πράττειν, ἀναγκαζόμεθα ἁμαρτάνειν αὐτοὶ πράττοντες. διὸ πάντα ἄνθρωπον χρὴ φεύγειν τὸ σφόδρα φιλεῖν αὑτόν, τὸν δʼ ἑαυτοῦ βελτίω διώκειν ἀεί, μηδεμίαν αἰσχύνην ἐπὶ τῷ τοιούτῳ πρόσθεν ποιούμενον.ἃ δὲ σμικρότερα μὲν τούτων καὶ λεγόμενα πολλάκις ἐστίν, χρήσιμα δὲ τούτων οὐχ ἧττον, χρὴ λέγειν ἑαυτὸν ἀναμιμνῄσκοντα· ὥσπερ γάρ τινος ἀπορρέοντος ἀεὶ δεῖ τοὐναντίον ἐπιρρεῖν, ἀνάμνησις δʼ ἐστὶν ἐπιρροὴ φρονήσεως ἀπολειπούσης.

we necessarily go wrong in doing them ourselves. Wherefore every man must shun excessive self-love, and ever follow after him that is better than himself, allowing no shame to prevent him from so doing. Precepts that are less important than these and oftentimes repeated—but no less profitable—a man should repeat to himself by way of reminder; for where there is a constant efflux, there must also be a corresponding influx, and when wisdom flows away, the proper influx consists in recollection;