Now, I would be the first to say that I'm scared of dying, but to be frank, I am even more scared of living forever. If you think about it, you would have to ask yourself, why would you want to? What would you do for eternity on earth? As the song says, "It's a small world after all" and it would probably only take a few lifetimes' worth of time to see all anyone would want to see. Sure, the human race could come up with new and exciting experiences, but there is the downside that you WILL see everyone you ever care about die in one way or another. Also, as much as we can come up with new ways of living and new technology and all that, eventually one would probably get bored or tired of life and want to move on. Without the possibility of ending your life, it would be a pretty nightmarish existence after that happens.
