Good, thought-provoking thread, Being 18, I obviously still have countless things I wish to accomplish with my life. The thought of an untimely death is certainly frightening to my, currently conscious, mind. I do not particularly fear a freak accident such as being hit by a bus or a suicide-bomb (not that I'm worried about that, just to demonstrate an instant death scenario) because at the exact moment that happens, my mind will cease to exist. I do not fear that, because if that were to happen there would be no feelings. My mind would cease to exist, and I would not encounter any of the feeling associated with my fear of death.
On the other hand, if I were to be diagnosed with a fatal disease tomorrow and given a timeline, I believe the sense of fear I would feel would be overwhelming and crippling. I would be forced to sit there while I knew that my life was ending, and I think I would go crazy. It's hard to say how these thoughts will change as I become an adult and (hopefully) live a fulfilling and meaningful life. When I am, say, 70 and have lived a full life and accomplished things I wished to accomplish with my life, I think the prospect of death may not be so terrifying. But as it stands right now I most definitely fear death.