xy

Variant translation: In some remote corner of the universe, poured out and glittering in innumerable solar systems, there once was a star on which clever animals invented knowledge. That was the highest and most mendacious minute of "world history" — yet only a minute. After nature had drawn a few breaths the star grew cold, and the clever animals had to die.
One might invent such a fable and still not have illustrated sufficiently how wretched, how shadowy and flighty, how aimless and arbitrary, the human intellect appears in nature. There have been eternities when it did not exist; and when it is done for again, nothing will have happened.
On Truth and Lie in an Extra-Moral Sense (1873)
Context: Once upon a time, in some out of the way corner of that universe which is dispersed into numberless twinkling solar systems, there was a star upon which clever beasts invented knowing. That was the most arrogant and mendacious minute of "world history," but nevertheless, it was only a minute. After nature had drawn a few breaths, the star cooled and congealed, and the clever beasts had to die. One might invent such a fable, and yet he still would not have adequately illustrated how miserable, how shadowy and transient, how aimless and arbitrary the human intellect looks within nature. There were eternities during which it did not exist. And when it is all over with the human intellect, nothing will have happened.

Source: Selected Letters

Source: Dithyrambs of Dionysus

Source: Thus Spoke Zarathustra

Source: Beyond Good and Evil

Gott ist tot! aber so wie die Art der Menschen ist, wird es vielleicht noch Jahrtausende lang Höhlen geben, in denen man seinen Schatten zeigt.
Und wir — Wir müssen auch noch seinen Schatten besiegen.
Sec. 108
Quotes about quotes: see also God is dead.
The Gay Science (1882)
Source: The Portable Nietzsche

Gegen die Langeweile kämpfen Götter selbst vergebens.
Sec. 48
The Antichrist (1888)
Source: The Anti-Christ

Source: Thus Spoke Zarathustra

Variant: The maturity of man—that means, to have reacquired the seriousness that one had as a child at play
Source: Beyond Good and Evil

Es ist nicht der Kampf der Meinungen, welcher die Geschichte so gewaltthätig gemacht hat, sondern der Kampf des Glaubens an die Meinungen, das heisst der Ueberzeugungen.
Section IX, "Man Alone with Himself" / excerpt from aphorism 630
Source: Human, All Too Human (1878), Helen Zimmern translation

Variant: Digressions, objections, delight in mockery, carefree mistrust are signs of health; everything unconditional belongs in pathology.