I find it easy to say now that I'm not scared of dying, but I'm not at all confident that I wouldn't be scared in extremis. Which is exactly why I want a tight living will, and why one of the clauses in it specifies that any decisions I make while competent are not to be construed as voiding any provisions of it.

One thing I know for sure about myself is that when I'm scared, I make bad decisions. And I know that I'm not brave, not strong, not capable of living the life that some people do. If I can pre-empt it, I'd rather be spared the decision. If I'm not going to recover the quality of life I specify in the living will, then let me bleed out, don't re-start my heart, whatever.