On the other hand, if our lives are repeated an infinite number of times, everything we do carries with it a great significance, a great weight of responsibility.
For this reason, Nietzsche calls the notion of eternal return "the heaviest of all burdens" (in German, of course).
If heaviness is such a drag, then it's wonderful that we live our lives only once – we get to be nice and light and responsibility-free.
But wait a second…is it really better to be light and responsibility-free?
Maybe not. Take sex, for example – women long to be pinned down by the weight of a man. Weight might mean responsibility, but it also means pleasure and fulfillment and meaning.
So which one is better – lightness or weight?
Parmenides, a philosopher in the sixth century BC, considered this question and decided that lightness was better.
But whether he was right or not remains to be seen.