Enchiridion · §21

θάνατος καὶ φυγὴ καὶ πάντα τὰ δεινὰ φαινόμενα πρὸ ὀφθαλμῶν ἔστω σοι καθ᾽ ἡμέραν, μάλιστα δὲ πάντων ὁ θάνατος· καὶ οὐδέποτε οὐδὲν ἀγεννὲς ἐνθυμηθήσῃ οὐδὲ λίαν ἐπιθυμήσεις τινός.

thanatos kai phugē kai panta ta deina phainomena pro ophthalmōn estō soi kath' hēmeran, malista de pantōn ho thanatos; kai oudepote ouden agennes enthumēthēsē oude lian epithumēseis tinos.

Let death and exile and everything that appears dreadful be daily before your eyes — above all, death. Then you will never think any mean thought, nor will you desire anything excessively.

— Enchiridion 21

Source: Greek (Schenkl/Oldfather critical edition tradition) + Long 1877 English translation