Philo, The Preliminary studies 29.166–7
There are those who, when they encounter the frights and horrors of the wilderness with complete endurance and strength complete the contest of life, after preserving it unsullied and unconquered, holding fast against the compulsions of nature like poverty, so that they subdue hunger, thirst, cold, and heat and everything which enslaves other people through the great abundance of their strength.
The cause of this is not simple toil but toil with a certain sweetening. For he says “the water is sweetened” and the work that is sweet and attractive is also called “love of labor” (philoponia). For in work the desire and longing and and love of finer things is sweet. Let no one turn away from this kind of suffering, nor let anyone believe that when the table of the feast and happiness is called “bread of suffering” it is for its harm rather than profit. For the soul which is chastened is fed by the instructions of education.”
οἱ δὲ τὰ φοβερὰ καὶ δεινὰ τῆς ἐρήμης πάνυ τλητικῶς καὶ ἐρρωμένως ἀναδεχόμενοι τὸν ἀγῶνα τοῦ βίου διήθλησαν ἀδιάφθορον καὶ ἀήττητον φυλάξαντες καὶ τῶν τῆς φύσεως ἀναγκαίων κατεξαναστάντες, ὡς πεῖναν, δίψος, [ῥῖγος,] κρύος, θάλπος, ὅσα τοὺς ἄλλους εἴωθε δουλοῦσθαι, κατὰ πολλὴν ἰσχύος περιουσίαν ὑπάγεσθαι. αἴτιον δὲ ἐγένετο οὐ ψιλὸς ὁ πόνος, ἀλλὰ σὺν τῷ γλυκανθῆναι· λέγει γάρ· “ἐγλυκάνθη τὸ ὕδωρ,” γλυκὺς δὲ καὶ ἡδὺς πόνος ἑτέρῳ ὀνόματι φιλοπονία καλεῖται. τὸ γὰρ ἐν πόνῳ γλυκὺ ἔρως ἐστὶ καὶ πόθος καὶ ζῆλος καὶ φιλία τοῦ καλοῦ. μηδεὶς οὖν τὴν τοιαύτην κάκωσιν ἀποστρεφέσθω, μηδ᾿ “ ἄρτον κακώσεως” νομισάτω ποτὲ λέγεσθαι τὴν ἑορτῆς καὶ εὐφροσύνης τράπεζαν ἐπὶ βλάβῃ μᾶλλον ἢ ὠφελείᾳ· τρέφεται γὰρ τοῖς παιδείας δόγμασιν ἡ νουθετουμένη ψυχή.