30 Phil, Chapter 30, Nietzsche, Touchstone 77: Eternal Recurrence.

The Eternal Recurrence is a thought experiment that urges you to live as though your life will repeat itself infinitely. It is designed to awaken a sense of urgency and existential responsibility. The potency of this idea lies in its call for radical responsibility; it compels you to sift through the empirical, rational, and even irrational elements of your life.