Laudator Temporis Acti

Horace, Epistles 1.4.12-14 (tr. John Conington):

Let hopes and sorrows, fears and angers be,
And think each day that dawns the last you'll see;
For so the hour that greets you unforeseen
Will bring with it enjoyment twice as keen.

Inter spem curamque, timores inter et iras,
omnem crede diem tibi diluxisse supremum;
grata superveniet quae non sperabitur hora.

See also:

• Horace, Epistles 1.11.22-23: Whatever time God has blessed you with, grasp with a grateful hand, and don't postpone pleasures for long (tu quamcumque deus tibi fortunaverit horam / grata sume manu, neu dulcia differ in annum).
  
• Horace, Odes 1.11.8: Seize the day, trusting as little as possible in tomorrow (carpe diem, quam minimum credula postero).
  
• Horace, Odes 2.16.25-26: The mind which rejoices in what is present, will be unwilling to worry about what is to come (laetus in praesens animus quod ultra est / oderit curare).
  
• Horace, Odes 3.8.27: With joy seize the gifts of the current hour (dona praesentis cape laetus horae).
  
• Petronius 99.1: I have always and everywhere lived in such a way that I spent each day as though it were my last and would never return (ego sic semper et ubique vixi ut ultimam quamque lucem tamquam non redituram consumerem).
  
• Edward Fitzgerald, The Rubaiyat of Omar Khayyam, stanza 21: Ah, my Beloved, fill the Cup that clears / TO-DAY of past Regrets and future Fears: / To-morrow! Why, To-morrow I may be / Myself with Yesterday's Sev'n thousand Years.
  
• Pascal, Pensées 203 (tr. W.F. Trotter): Let us act as if we had only eight hours to live.