I am insanely terrified of death. The inevitability, the uncertainty, and the finality around the concept have led me to lose sleep on far too many occaisions.
You didn't exist before you were born. Does that trouble you?
Not the one you asked, but it troubles me in the sense that it's impossible to comprehend.
Although the Christian afterlife setup is horrible. Not only do most people end up suffering for somewhat arbitrary reasons (not believing in a book in just the right way), but those lucky few that make the right guess do something that also sounds bad--so you want me to worship a deity I never believed in and don't really like...eternally? Frankly I'd prefer this crappy life to Heaven, at least it's
sometimes interesting and I can...er..."relax" in a certain way moral puritans would not approve of.