Hmm, hard to choose one. But this is one of my favorites: (from Pensées, Blaise Pascal)

"L'homme n'est qu'un roseau, le plus faible de la nature; mais c'est un roseau pensant. Il ne faut pas que l’univers entier s’arme pour l’écraser : une vapeur, une goutte d’eau suffit pour le tuer. Mais quand l’univers l’écraserait, l’homme serait encore plus noble que ce qui le tue, parce qu’il sait qu’il meurt, et l’avantage que l’univers a sur lui, l’univers n’en sait rien."


Translation:

"Man is but a reed, the most feeble thing in nature; but he is a thinking reed. The entire universe need not arm itself to crush him. A vapour, a drop of water suffices to kill him. But, if the universe were to crush him, man would still be more noble than that which killed him, because he knows that he dies and the advantage which the universe has over him; the universe knows nothing of this."