That which we cannot truly explain is what we fear. Life can be explained through living it, we know what it means to be alive. But death? How can we fathom death? How is it to simply not exist any longer? That is why we fear it, because we cannot truly comprehend being dead. Those that can, obviously, don't fear it.
This line of thinking breeds the question that also needs to be answered by a polling of the various views represented in our menagerie - what do you think happens at and after the moment of death? Heaven, hell, oblivion? Do tell...
That, my dear, would be impossible. Fear, as cited, is a part of life... fear of death, of pain, of loss. You could not, as you say, live life to the fullest if your existence was perpetual without concern of demise.
And further implies that since, I assume, you will one day die, hence; can die - you are not living your life to the fullest as it stands.
My argument, at its core, is simple. We cannot hope to have the wisdom or knowledge to make an informed choice about immortality and that being the case, admit the very real potential that, in so doing, one would long lament their choice.
If there were an election tomorrow, would you vote? If you answered yes, you do a disservice to the truth of democracy for, in that brief window, one could not hope to be properly informed and so make thus an informed choice regarding your vote.
The same, I feel, stands for the question at hand.
When we are eighty years old, well in to our declining years, I think our choices would be much different. Keeping in mind the average youthful age of members here-abouts.
That is not to say that I would not support anyone in making such a decision, it's simply not for me and I believe it with such vehemency that, concerned for those I care about and the direction of human sociology, I would attempt to dissuade someone from it before hand.
This discussion is truly interesting, I find.
I do not know, nor could I pretend to. However, I hope for something beyond the agnostic approach - the body rots, the person gone. I, believing in the prevailing laws of physics regarding matter and energy, chose instead to believe that the energy patterns that grant us consciousness instead continue in some fashion.
In that moment of death, it has been postulated, the human psyche undergoes a change - where in that moment between life and death expands in to the infinite.