Plato, Laws 903d

ὅλον μέρους ἕνεκα ἀπεργάζεται· σὺ δὲ ἀγανακτεῖς, ἀγνοῶν ὅπῃ τὸ περὶ σὲ ἄριστον τῷ παντὶ συμβαίνει καὶ σοὶ κατὰ δύναμιν τὴν τῆς κοινῆς γενέσεως. ἐπεὶ δὲ ἀεὶ ψυχὴ συντεταγμένη σώματι τοτὲ μὲν ἄλλῳ, τοτὲ δὲ ἄλλῳ, μεταβάλλει παντοίας μεταβολὰς διʼ ἑαυτὴν ἢ διʼ ἑτέραν ψυχήν, οὐδὲν ἄλλο ἔργον τῷ πεττευτῇ λείπεται πλὴν μετατιθέναι τὸ μὲν ἄμεινον γιγνόμενον ἦθος εἰς βελτίω τόπον, χεῖρον δὲ εἰς τὸν χείρονα, κατὰ τὸ πρέπον αὐτῶν ἕκαστον, ἵνα τῆς προσηκούσης

but thou art vexed, because thou knowest not how what is best in thy case for the All turns out best for thyself also, in accordance with the power of your common origin. And inasmuch as soul, being conjoined now with one body, now with another, is always undergoing all kinds of changes either of itself or owing to another soul, there is left for the draughts-player no further task,—save only to shift the character that grows better to a superior place, and the worse to a worse, according to what best suits each of them, so that to each may be allotted its appropriate destiny.