Yes, I know what you mean. Just the thought of that relief of no more worries, no more trying, no more pain is incredibly appealing. More appealing than anything life seems to offer.
Hmmm, have you really questioned what it is that's holding you back? I think for a lot of us, it is fear of the process itself- obtaining everything needed for our chosen method in the first place and the intense worry that it might fail.
Still, if it's the 'finality of death' that is troubling you- maybe there are still things you want to do/ experience while you are still alive?
It's not a fear that is easy to comfort I'm afraid. I suppose there's the reasoning that death happens to everyone at some point and when it's happened (depending on your belief system) you'll no longer be worrying or afraid of anything.
Like the previous post said though, I have a feeling that people kind of know when it is there time to go- perhaps when the fears they have seem slightly less than the desire to get the hell out. I wish you all the best- whatever you decide to do.