Never resent the enemy. Marcus Aurelius 5.20

Marcus here reflects on the power of the mind to overcome obstacles, including opposition that we encounter from other people. He would approach such opposition no differently than if it came from bad weather, or wild animals. When fate forced his hand, he stayed true to these principles: instead of resenting his wife for her role in the rebellion of Avidius Cassius (175 CE), he forgave her freely, and used only necessary force to put down that rebellion. No resentment or recrimination; just business. Contrast this with the behavior of the ancient Persian king Xerxes, who supposedly had the waters of the Hellespont whipped after a storm interrupted his troops' attempt to cross (480 BCE, cf. Herodotus 7.35). He was not indifferent to weather! Or to mankind, for that matter. 

Καθ’ ἕτερον μὲν λόγον ἡμῖν ἐστιν οἰκειότατον ἄνθρωπος, καθ’ ὅσον εὖ ποιητέον αὐτοὺς καὶ ἀνεκτέον· καθ’ ὅσον δὲ ἐνίστανταί τινες εἰς τὰ οἰκεῖα ἔργα, ἕν τι τῶν ἀδιαφόρων μοι γίνεται ὁ ἄνθρωπος οὐχ ἧσσον ἢ ἥλιος ἢ ἄνεμος ἢ θηρίον. ὑπὸ τούτων δὲ ἐνέργεια μέν τις ἐμποδισθείη ἄν, ὁρμῆς δὲ καὶ διαθέσεως οὐ γίνεται ἐμπόδια διὰ τὴν ὑπεξαίρεσιν καὶ τὴν περιτροπήν. περιτρέπει γὰρ καὶ μεθίστησι πᾶν τὸ τῆς ἐνεργείας κώλυμα ἡ διάνοια εἰς τὸ προηγούμενον καὶ πρὸ ἔργου γίνεται τὸ τοῦ ἔργου τούτου ἐφεκτικὸν καὶ πρὸ ὁδοῦ τὸ τῆς ὁδοῦ ταύτης ἐνστατικόν. 

By one way of reckoning, mankind is the most familiar thing we know, and other people must be treated well and endured patiently. But as certain people resist the pull of familiar things, so to me mankind exists without distinction, no different from the sun, the wind, or wild animals. If any of these latter were to check me on my path, I would not hesitate to remove or overcome the obstacle presented. For the mind refutes and removes every impediment to its activity, serving the purpose it has conceived: it becomes the only effective check on any task it undertakes, the only intractable obstacle on the course that it pursues.