Letter 858: Anger is a fire: useful when controlled, devastating when unleashed.

To Agathodaimon. Even if to certain people, perhaps those who flatter you, your reply seemed to be the product of reason and not of anger, to me its fruit seems to belong rather to insolence than to boldness. Therefore I urge you to place reason before anger, and in this way both to speak and to write. For if you should permit it [anger] to leap out ahead of reason, it will turn everything upside down.

Εἰ καί τισιν ἴσως κολακεύουσί σε, ἔδοξε λογισμοῦ εἶναι, οὐκ ὀργῆς ἡ ἀπόκρισις, ἐμοὶ δοκεῖ θρασύτητος μᾶλλον εἶναι ἢ θράσους ὁ καρπός. Διὸ δὴ παραινῶ σοι ἔμπροσθεν τῆς ὀργῆς τιθέναι τὸν λογισμόν, καὶ οὕτω καὶ λέγειν καὶ γράφειν. Εἰ γὰρ συγχωρήσειας αὐτῇ προπηδᾷν τοῦ λογισμοῦ, πάντα ἄνω καὶ κάτω ποιήσει.