δυσθυμεῖσθαι
From LSJ
πάντες γὰρ οἱ λαβόντες μάχαιραν ἐν μαχαίρῃ ἀπολοῦνται → all they that take the sword shall perish with the sword
Greek > English (Woodhouse Verbs Reversed)
(see also δυσθυμέω): dejected, be cast down, be dejected, be depressed, be melancholy, be moody, be sad, be sorrowful, be disheartened