I'm scared of there being nothing after death. I mean, how can we just not be anywhere all of a sudden? It freaks me out. I sit awake, and i will all of a sudden get the horrible feeling you were describing. I can't stand the thought of not being here, even if Earth isn't the nicest place! I guess you just have to accept it, and try to live your life like you want, and be happy. I realised a long time ago there's no point living in fear of death, because then you'll be dead inside anyway.
I believe there is no reason we are here, and that we should just live without worrying about the inevitable.