Life is so sweet! One can die but once, and it is for such a long time!

[Il est si doux de vivre: On ne meurt qu’une fois; et c’est pour si long-tems (longtemps)!]

Molière (1622–1673) French playwright, actor [stage name for Jean-Baptiste Poquelin]

The Love-Tiff [Le Dépit Amoureux], Act 5, sc. 4 (1656) [tr. Van Laun (1875)]
    (Source)

Other translations: "Life is so sweet! We die only once, and for such a long time!" [Lovers' Quarrels, tr. Wall (1879)]

Original French text.