Seneca, Letters to Lucilius, 1.1:
“Act thus, my Lucilius: justify yourself, collect and save all of the time which to this point has been taken off, or stolen, or simply slipped away. Persuade yourself that the matter stands as I write: some time is stolen from us, some is drawn off, and some just flows away. The most shameful loss, though, is the one which occurs through negligence. If you wish to take note, you will see that a large part of life slips away from those who act badly, the greatest portion slips away from those who do nothing, and all of life slips away from those who are busy doing something else. What person can you cite who places a price upon his time, who takes an account of the day, who understands that he is dying every day? We are deceived in this, that we look forward to death: a large part of it has already gone by, and whatever part of our lives is in the past is death’s property now. Therefore, act as you claim to do, and embrace every hour; thus it will happen that you weigh out less of tomorrow, if you throw your hand upon today. Life runs away when it is delayed. All things, my Lucilius, are foreign to us: time alone is ours. Nature has granted us the possession of this one fleeting, slippery thing, from which she expels whoever wishes it. The stupidity of humans is so great that they allow the smallest, most worthless things (certainly, those which can be retrieved) to be added to their account when they have accomplished them, but no one thinks that he owes any debt when he receives time, though this is the one thing which no one is able to pay back readily.
You will perhaps ask how I act, I who deliver these precepts to you. I will confess honestly: as happens among the diligent partaker of luxury, I keep an account of the cost. I can not say that I have wasted nothing, but I can give an account of why and how I wasted it. I will explain the causes of my poverty. But it happens to me as to many who have been reduced to poverty through no fault of their own: all ignore him, no one helps him. What then? I do not consider a man poor if whatever is left to him seems enough to him. I advise you, though to hold on to what is yours, and do it in good time. For, as the ancients say, ‘Parsimony is too late on the ground,’ for not only is the remaining portion at the bottom the smallest, but it is also the worst. Goodbye.”
Ita fac, mi Lucili: vindica te tibi, et tempus quod adhuc aut auferebatur aut subripiebatur aut excidebat collige et serva. Persuade tibi hoc sic esse ut scribo: quaedam tempora eripiuntur nobis, quaedam subducuntur, quaedam effluunt. Turpissima tamen est iactura quae per neglegentiam fit. Et si volueris attendere, magna pars vitae elabitur male agentibus, maxima nihil agentibus, tota vita aliud agentibus.  Quem mihi dabis qui aliquod pretium tempori ponat, qui diem aestimet, qui intellegat se cotidie mori? In hoc enim fallimur, quod mortem prospicimus: magna pars eius iam praeterit; quidquid aetatis retro est mors tenet. Fac ergo, mi Lucili, quod facere te scribis, omnes horas complectere; sic fiet ut minus ex crastino pendeas, si hodierno manum inieceris.  Dum differtur vita transcurrit. Omnia, Lucili, aliena sunt, tempus tantum nostrum est; in huius rei unius fugacis ac lubricae possessionem natura nos misit, ex qua expellit quicumque vult. Et tanta stultitia mortalium est ut quae minima et vilissima sunt, certe reparabilia, imputari sibi cum impetravere patiantur, nemo se iudicet quicquam debere qui tempus accepit, cum interim hoc unum est quod ne gratus quidem potest reddere.
 Interrogabis fortasse quid ego faciam qui tibi ista praecipio. Fatebor ingenue: quod apud luxuriosum sed diligentem evenit, ratio mihi constat impensae. Non possum dicere nihil perdere, sed quid perdam et quare et quemadmodum dicam; causas paupertatis meae reddam. Sed evenit mihi quod plerisque non suo vitio ad inopiam redactis: omnes ignoscunt, nemo succurrit.  Quid ergo est? non puto pauperem cui quantulumcumque superest sat est; tu tamen malo serves tua, et bono tempore incipies. Nam ut visum est maioribus nostris, ‘sera parsimonia in fundo est’; non enim tantum minimum in imo sed pessimum remanet. Vale.