When I was a child the priest on Sunday said that we'd go to hell or heaven when we die and that we'd stay there forever. I got very scared, I don't want to exist forever, I find that a very scary thought.
Later once I grew up I realized that there is probably no god, so this is a non-issue for me now.
Does that not make you want to enjoy every moment of your life to the fullest? If it's the only one you get then you might as well spend it doing things that make you happy.
Personally, I find all the other eschatological possibilities much more disturbing. The heaven/hell dichotomy is unnerving on a lot of obvious levels. Reincarnation seems fraught with neverending suffering. And the idea of becoming a "ghost" or a spirit, forever consigned to haunt some old place is as terrible as it is ridiculous.
I'm looking forward to my hard earned non-existence, thank you very much.