No advice, but Davidson Loehr's story of a man who had said he didn't want to be kept alive if he had a massive paralyzing stroke, and who then had that stroke, has stuck with me ever since I heard that sermon.
(http://www.austinuu.org/wp/2004/10/on-death-and-dying/ (http://www.austinuu.org/wp/2004/10/on-death-and-dying/) , about 5/6 down the page)