Mark Twain put it pithily (and perhaps apocryphally): "I do not fear death. I had been dead for billions and billions of years before I was born, and had not suffered the slightest inconvenience from it."
Apparently there's a name for this: the Lucretian symmetry argument. And I recently learned there are philosophers who argue the asymmetry in our attitudes is actually rational, and that fearing death while not fearing pre-natal nonexistence makes sense [1].
I find comfort in treating the two as being equal, and I'd be lying if I said I'm not a little hesitant to read their case.
[1] https://link.springer.com/chapter/10.1007/978-94-015-9868-2_...