This thread seems to have three aspects: theological, practical, and ethical. I will start with the theological
I'm 24 years old. I've barely lived at all. I'm not going to check out early if I can help it at all.
...
I think if you believe in an afterlife you can't possibly contemplate what it is like to be in my position.
You think incorrectly. I've given the concept a great deal of thought. What is amazing is that you aren't paralyzed by fear. You know you will die someday. You believe you will cease to exist at that point. You know there's nothing you can do to stop it. That's the worst hell I can imagine.
If you've always believed there is something after death, then you cannot know what it is like for those who just cannot believe in an afterlife. The way it changes how you feel about death is huge, and you're right, it is hell (but a hell you can't understand unless you believe that everything about you will cease to exist at death)...
I'm in the same ontological/epistomological boat as Sas, but being 38 instead of 24, I've had 14 more years and had a best friend die and had to try to wrap my head around the whole problem.
At some point you just realize that everything naturally has to have an end, and so do you, and you get acceptance of that fact.
And, actually given that we're a supposedly christian/religious nation believing in a heavenly afterlife, we sure do fear death a whole lot. Having at least knocked mine back a lot, most of our society seems to be infected with an irrational fear of death and inability to accept it as a natural process -- and it doesn't really seem to differ between atheists/agnostics and religious people.
That's probably part of it. That I can't fully imagine what it is like to not exist. I would imagine 15 years being raised in a very strict Christian family has warped my subconscious a bit too in that I was always taught that I could expect something after death, but now that I don't believe there is, it has meant a huge loss to me. (Believe me the benefits outweigh the negatives of this, but there definitely have been some downsides)
Like Sas, I was raised in a strict Christian upbringing. I even considered the ministry. Oddly enough, it was my close study of religious concepts that led me to abandon those beliefs. I know well the fear she describes. I used to lie awake at night thinking about it.
I was so interested in those feelings that I made it a bit of a study, and I learned that there is a pattern that almost everyone goes through--religious or not. Lamont's fine post can be summarized by an old Albert King blues song:
Everybody want to go to heaven, but nobody wants to die. John Donne, while dying, thought about this in one of his best meditations, in which he observed his fear that the doctor examining him was seeing signs of close death, when he should be greeting such signs with joy of an imminent afterlife.
My fears peaked at about age 35, roughly the same age at which Shakespeare penned his magnificent examination of the certainty of death,
Hamlet. After that, like Walter and Lamont, those fears subsided to the point that they don't matter to me at all any more. I think that pattern is close to universal.
So I do know how someone with that belief system feels, and I don't think it is all that much different from what a person with another belief system feels.
I will blend this with my post on ethics.