I think coming to terms that we are a biological life-form like any other is an important part of everyone's existence. Everyone here is going to die eventually. No there is no way around it. Nothing you can do is going to prevent getting old or prevent dying. There are two ways to go about this. 1, you realize this and age gracefully, not fighting biology, and embracing every new chapter in your life. 2, you can try and fight it by glorifying youth and fighting your constant aging. If you go with the second route, you might be one of those creepy dudes in their late 40's that wears the same clothes that 15yo's wear, and goes to high school and college parties. Seriously, those guys are creepy. You can also fight it by constantly having plastic surgery, which is discusting because everyone can tell when you have too much plastic surgery, or good forbid, the doctor doesn't do very well.
That being said, I don't really want to get so old I need other people to take care of me, or I can't work anymore. I think when it comes down to that point, I might just reignite my opiate addiction and have some fun for a few weeks / months, until I gather my family around to say good bye, and go to sleep forever. This may be at 45 if I'm terribly ill, or injured, but will probably be later.
I recently had a quarter life crisis, I do have a severe illness that might make me an invalid significantly earlier than most people. I also have some permanent injuries that make certain tasks very difficult. I didn't want to live anymore. I realized that as much as these things suck, I'm still able to function as well as most people, even though I can't do a lot of things I could do at 20 (I'm 25).
I'm going to die, your going to die, we all are going to die, and we have no idea when. We must do our best to leave this Earth in better condition than when we got it. Then make room for those babies being born right now, and in the future, because it will be their turn to live (and then die).
For those who think they are going to die very young and think they haven't accomplished anything... Well your really young, of course you haven't done anything, you still have 3-4x as many years as you've already had. Even if you don't do something truly great and get in the history books, you can still do something great. Bringing other people into this world and providing a nice, stable, home for youngsters to grow is just as important as becoming a famous politician or whatever you consider "doing something with you life."