Marcus Aurelius, Meditations 4.2

μηδὲν ἐνέργημα εἰκῇ μηδὲ ἄλλως ἢ κατὰ θεώρημα συμπληρωτικὸν τῆς τέχνης ἐνεργείσθω.

No action should be done at random, nothing other than what is an essential part of the system.

Marcus Aurelius, Meditations 2.1

ἕωθεν προλέγειν ἑαυτῷ· συντεύξομαι περιέργῳ, ἀχαρίστῳ, ὑβριστῇ, δολερῷ, βασκάνῳ, ἀκοινωνήτῳ· πάντα ταῦτα συμβέβηκεν ἐκείνοις παρὰ τὴν ἄγνοιαν τῶν ἀγαθῶν καὶ κακῶν.

First thing in the morning say to yourself: ‘I’m going to meet a busybody, an ingrate, a bighead, a fraudster, a slanderer, and an anti-social person; they’ve become all these things because of their ignorance of good and evil.’

Marcus Aurelius, Meditations 7.49

τὰ προγεγονότα ἀναθεωρεῖν, τὰς τοσαύτας τῶν ἡγεμονιῶν μεταβολάς. ἔξεστι καὶ τὰ ἐσόμενα προεφορᾶν· ὁμοειδῆ γὰρ πάντως ἔσται καὶ οὐχ οἷόν τε ἐκβῆναι τοῦ ῥυθμοῦ τῶν νῦν γινομένων, ὅθεν καὶ ἴσον τὸ τεσσαράκοντα ἔτεσιν ἱστορῆσαι τὸν ἀνθρώπινον βίον τῷ ἐπὶ ἔτη μύρια· τί γὰρ πλέον ὄψει;

Contemplate the events of the past – such great changes in political supremacies – and it becomes possible to foresee the events of the future. For they will be of just the same forms, and cannot turn out differently from the pattern of events happening in the present; therefore observing human life for forty years is the same as for ten thousand years. What more will you see?

Marcus Aurelius, Meditations 6.19

μή, εἴ τι αὐτῷ σοὶ δυσκαταπόνητον, τοῦτο ἀνθρώπῳ ἀδύνατον ὑπολαμβάνειν, ἀλλ’ εἴ τι ἀνθρώπῳ δυνατὸν καὶ οἰκεῖον, τοῦτο καὶ σεαυτῷ ἐφικτὸν νομίζειν.

If something is exceedingly hard for you to do, don’t suppose that it is impossible for a human, but if it is something possible and suitable for a human, think that it is within your power as well.