"What, if some day or night a demon were to steal after you into your loneliest loneliness and say to you: "This life as you now live it and have lived it, you will have to live once more and innumerable times more; and there will be nothing new in it, but every pain and every joy and every thought and sigh and everything unutterably small or great in your life will have to return to you, all in the same succession and sequence—even this spider and this moonlight between the trees, and even this moment and I myself. The eternal hourglass of existence is turned upside down again and again, and you with it, speck of dust!"
Would you not throw yourself down and gnash your teeth and curse the demon who spoke thus? Or have you once experienced a tremendous moment when you would have answered him: "You are a god and never have I heard anything more divine." If this thought gained possession of you, it would change you as you are or perhaps crush you. The question in each and every thing, "Do you desire this once more and innumerable times more?" would lie upon your actions as the greatest weight. Or how well disposed would you have to become to yourself and to life to crave nothing more fervently than this ultimate eternal confirmation and seal?"
-Friedrich Nietzsche, The Gay Science
You turn man back to the dust,
and say, "Turn back, O children of men!"
For a thousand years in your sight
are but as yesterday when it is past,
or as a watch in the night.
You sweep men away;
they are like a dream,
like grass which is renewed in the morning:
in the morning it flourishes and is renewed;
in the evening it fades and withers.
So teach us to number our days
that we may get a heart of wisdom.
Return, O LORD! How long?
Have pity on your servants!
Satisfy us in the morning with your steadfast love,
that we may rejoice and be glad all our days.
Let the favor of the Lord our God be upon us,
and establish the work of our hands upon us,
yes, the work of our hands establish it.
-Psalm 90:3-6,12-14,17