https://en.wikipedia.org/wiki/Vertiginous_question
Benj Hellie’s vertiginous question asks why, of all the subjects of experience out there, this one—the one corresponding to the human being referred to as Benj Hellie—is the one whose experiences are live? (The reader is supposed to substitute their own case for Hellie’s.)
This question has already been answered. Intuitively, you can ask “why am I a human instead of a fish?”
That’s symmetrical with: if a future version of yourself was convinced that it deserved to not exist forever, you would infinitely prefer that your future self be unsatisfied than have its (“your”) new existence terminated.
Minimizing suffering (NegUtilism) is an arbitrary moral imperative. A moral imperative to maximize happiness (PosUtilism) is at least as valid.