ἀβίωτόν ἐστι

From LSJ

νέῳ δὲ σιγᾶν μᾶλλον ἢ λαλεῖν πρέπει → it's fitting for a young man to keep silence rather than to speak (Menander)

Source

Greek > English (Woodhouse)

life is a blank, life is not worth living