From Plutarch’s How a Man May Become Aware of his Progress in Virtue – volume 1 of the Loeb Moralia (pg 409).
If therefore you follow the advice given by the god in the oracle, to “fight the Cirrhaeans all days and all nights,” and are conscious that you likewise in the daytime and the nighttime have always carried on an unrelenting warfare against vice, or at least that you have not often relaxed your vigilance nor constantly granted admission to divers pleasures, recreations, and pastimes, which are, as it were, envoys sent by vice to treat for a truce, it is then quite probable that you may go on with good courage and confidence to what still remains.
However, even though it be that intermissions occur in one’s philosophical studies, yet if the later periods of study are more constant and long-continued than they were earlier, this is no slight indication that the spirit of indifference is being expelled through industry and practice; but there is something pernicious in the opposite condition, when numerous and continued set-backs occur after no long time, as if the spirit of eagerness were withering away. We may compare a reed, the growth of which at its beginning has a very great impetus, which results in an even and continuous length, at first in long sections, since it meets with few obstacles and repulses, but later, as though for lack of breath as it gets higher up, it grows weak and weary, and is gathered up in the many frequent nodules, when the life-giving spirit meets with buffets and shocks; so with philosophy, those who at the outset engage in long excursions into its realms and later meet with a long series of obstacles and distractions without becoming aware of any change toward the better, finally get wearied out, and give up. But a man of the other type “is again given wings” by the help he gets as he is carried onward, and by the strength and eagerness born of successful accomplishment brushes aside pretences as though they were a hindering crowd in his path. In the same way that an indication of the beginning of love is to be found, not in the taking delight in the presence of the loved one (for this is usual), but in feeling a sting of pain when separated; just so are many allured by philosophy and seem to take hold of the task of learning with high aspirations, but if they are forced by other business and occupations to leave it, all that excitement of theirs subsides and they no longer care. But he in whose heart the prick of youthful love is planted may appear to you moderate and mild while present at philosophical discussions; but when he is separated and apart from them, behold him ardent and troubled, and dissatisfied with all business and occupations, and, cherishing the mere recollection, he is driven about like an irrational being by his yearning towards philosophy. For we ought not to enjoy being present at discussions as we enjoy the presence of perfumes, and then when we are removed from them not seek after them or even feel uneasy; but we ought in our periods of separation to experience a sensation akin in a way to hunger and thirst, and so be led to cleave to what makes for real progress, whether it chance to be a wedding or wealth or the duties of friendship or military service that causes the temporary parting. For the greater the acquisition from philosophy is, the more annoyance there is in being cut off from it.
ἂν οὖν κατὰ τὸν δοθέντα χρησμὸν ὑπὸ τοῦ θεοῦ “Κιρραίοις πάντ᾿ ἤματα καὶ πάσας νύκτας πολεμεῖν” οὕτω συνειδῇς σεαυτὸν ἡμέρας τε καὶ νύκτωρ ἀεὶ τῇ κακίᾳ διαμεμαχημένον, ἢ μὴ πολλάκις γε τὴν φρουρὰν ἀνεικότα μηδὲ συνεχῶς παρ᾿ αὐτῆς οἱονεὶ κήρυκας ἡδονάς τινας ἢ ῥᾳστώνας ἢ ἀσχολίας ἐπὶ σπονδαῖς προσδεδεγμένον, εἰκότως ἂν εὐθαρσὴς καὶ πρόθυμος βαδίζοις ἐπὶ τὸ λειπόμενον.
Οὐ μὴν ἀλλὰ κἂν ᾖ διαλείμματα γιγνόμενα τοῦ φιλοσοφεῖν, τὰ δ᾿ ὕστερα τῶν πρότερον ἑδραιότερα καὶ μακρότερα, σημεῖον οὐ φαῦλόν ἐστιν ἐκθλιβομένης πόνῳ καὶ ἀσκήσει τῆς ῥᾳθυμίας· τὸ δ᾿ ἐναντίον πονηρόν, αἱ μετ᾿ οὐ πολὺν χρόνον πολλαὶ καὶ συνεχεῖς ἀνακοπαί, τῆς προθυμίας οἷον ἀπομαραινομένης. ὡς γὰρ ἡ τοῦ καλάμου βλάστησις, 77ὁρμὴν ἔχουσα πλείστην ἀπ᾿ ἀρχῆς εἰς μῆκος ὁμαλὸν καὶ συνεχές, τὸ πρῶτον ἐν διαστήμασι μεγάλοις ὀλίγας λαμβάνουσα προσκρούσεις καὶ ἀντικοπάς, εῖθ᾿ οἷον ὑπ᾿ ἄσθματος ἄνω δι᾿ ἀσθένειαν ἀπαγορεύουσα πολλοῖς ἐνίσχεται καὶ πυκνοῖς τοῖς γόνασι, τοῦ πνεύματος πληγὰς καὶ τρόμους λαμβάνοντος, οὕτως ὅσοι τὸ πρῶτον μεγάλαις ἐκδρομαῖς ἐχρήσαντο πρὸς φιλοσοφίαν, εἶτα πολλὰ καὶ συνεχῆ προσκρούματα καὶ διασπάσματα λαμβάνουσι μηδενὸς Bδιαφόρου πρὸς τὸ βέλτιον ἐπαισθανόμενοι, τελευτῶντες ἐξέκαμον καὶ ἀπηγόρευσαν. “τῷ δ᾿ αὖτε πτερὰ γίγνετο” δι᾿ ὠφέλειαν φερομένῳ καὶ διακόπτοντι τὰς προφάσεις ὥσπερ ὄχλον ἐμποδὼν ὄντα ῥώμῃ καὶ προθυμίᾳ τῆς ἀνύσεως. καθάπερ οὖν ἔρωτος ἀρχομένου σημεῖόν ἐστιν οὐ τὸ χαίρειν τῷ καλῷ παρόντι (τοῦτο γὰρ κοινόν) ἀλλὰ τὸ δάκνεσθαι καὶ ἀλγεῖν ἀποσπώμενον, οὕτως ἄγονται μὲν ὑπὸ φιλοσοφίας πολλοὶ καὶ σφόδρα γε φιλοτίμως ἀντιλαμβάνεσθαι τοῦ μανθάνειν δοκοῦσιν, ἂν δ᾿ ἀπελαθῶσι ὑπὸ πραγμάτων ἄλλων καὶ ἀσχολιῶν, ἐξερρύη τὸ πάθος αὐτῶν ἐκεῖνο, καὶ ῥᾳδίως φέρουσιν.
ὅτῳ δ᾿ ἔρωτος δῆγμα παιδικῶν
πρόσεστι, μέτριος μὲν ἄν σοι φανείη καὶ πρᾶος ἐν τῷ παρεῖναι καὶ συμφιλοσοφεῖν ὅταν δ᾿ ἀποσπασθῇ καὶ χωρὶς γένηται, θεῶ φλεγόμενον καὶ ἀδημονοῦντα καὶ δυσκολαίνοντα πᾶσι πράγμασι καὶ ἀσχολίαις, μνήμην δὲ φιλῶν ὧσπερ ἄλογος ἐλαύνεται πόθῳ τῷ πρὸς φιλοσοφίαν. οὐ γὰρ δεῖ τοῖς λογοις εὐφραίνεσθαι μὲν παρόντας ὥσπερ τοῖς μύροις, ἀποστάντας δὲ μὴ ζητεῖν μηδ᾿ ἀσχάλλειν, ἀλλὰ πείνῃ τινὶ καὶ δίψῃ πάθος ὅμοιον ἐν τοῖς ἀποσπασμοῖς πάσχοντας ἔχεσθαι τοῦ προκόπτοντος ἀληθῶς, ἄν τε γάμος ἄν τε πλοῦτος ἄν τε φιλία τις ἄν τε στρατεία Dπροσπεσοῦσα ποιήσῃ τὸν χωρισμόν. ὅσῳ γὰρ πλέον ἐστὶ τὸ προσειλημμένον ἐκ φιλοσοφίας, τοσούτῳ πλέον ἐνοχλεῖ τὸ ἀπολειπόμενον.