διαφυλακτέον

From LSJ

νᾶφε καὶ μέμνασο ἀπιστεῖν → keep a clear head and remember not to believe a thing (Epicharmus fr. 250)

Source

Spanish (DGE)

hay que conservar, hay que mantener τὰ καθεστῶτα Anaximen.Rh.1423a31
hay que mantener, hay que prolongar τοὺς ... ἱδρῶτας Orib.5.30.27.