Σκηνὴ πᾶς ὁ βίος καὶ παίγνιον: ἢ μάθε παίζειν, τὴν σπουδὴν μεταθείς, ἢ φέρε τὰς ὀδύνας → All life is a stage and a play: either learn to play laying your gravity aside, or bear with life's pains.
credulous: P. εὐεξαπάτητος.
simple: P. and V. εὐήθης; see also guileless.