Seneca, Letters to Lucilius
24.19-20 (tr. Richard M. Gummere):
I remember one day you were handling the well-known commonplace,—that we do not suddenly fall on death, but advance towards it by slight degrees; we die every day. For every day a little of our life is taken from us; even when we are growing, our life is on the wane. We lose our childhood, then our boyhood, and then our youth. Counting even yesterday, all past time is lost time; the very day which we are now spending is shared between ourselves and death. It is not the last drop that empties the water-clock, but all that which previously has flowed out; similarly, the final hour when we cease to exist does not of itself bring death; it merely of itself completes the death-process. We reach death at that moment, but we have been a long time on the way.
memini te illum locum aliquando tractasse, non repente nos in mortem incidere, sed minutatim procedere; cotidie morimur. cotidie enim demitur
aliqua pars vitae, et tunc quoque, cum crescimus, vita decrescit. infantiam amisimus, deinde pueritiam, deinde adulescentiam. usque ad hesternum, quicquid transît temporis, perît; hunc ipsum, quem
agimus, diem cum morte dividimus. quemadmodum clepsydram non extremum stillicidium exhaurit, sed quicquid ante defluxit, sic ultima hora, qua esse desinimus, non sola mortem facit, sed sola consummat; tunc ad illam pervenimus, sed diu venimus.
Hat tip: Eric Thomson.