ἐξασκητέον
From LSJ
οἱ τοῖς πέλας ἐπιβουλεύοντες, λανθάνουσι πολλὰκις ὑφ' ἑτέρων τοῦτ' αὐτὸ πάσχοντες → when people plot against their neighbours, they fall victim to the same sort of plot themselves
English (LSJ)
A one must practise, σωφροσύνην Nicostr. ap. Stob. 4.23.65.