Cicero, On Old Age
23.85 (tr. William Armistead Falconer):
Again, if we are not going to be immortal, nevertheless, it is desirable for a man to be blotted out at his proper time. For as Nature has marked the bounds of everything else, so she has marked the bounds of life. Moreover, old age is the final scene, as it were, in life's drama, from which we ought to escape when it grows wearisome and, certainly, when we have had our fill.
quod si non sumus immortales futuri, tamen exstingui homini suo tempore optabile est. nam habet natura, ut aliarum omnium rerum, sic vivendi modum. senectus autem aetatis est peractio tamquam fabulae, cuius defetigationem fugere debemus, praesertim adiuncta satietate.