Generally, I'm not afraid. But sometimes, for a few brief moments, I'm absolutely terrified of dying, of everything being over before I've done all I want to do, that I'll leave my children behind and not know what became of them, etc. Doesn't last long, but it's very poignant.
"Death is a friend of ours. And he that is not ready to great him, is not at home." -Francis Bacon (I think )