I think it is okay. Death is the end result for everyone. I don't want to lose my self and not remember my kids or grand kids when I see them like my grandma did, or be some burden. I agree with Mr Pratchett. I had a friend who lived with brain cancer for over 20 years until he had had enough. He felt he had deteriorated too far to live his life as he saw fit. He took his life, his family was relived he was out of pain. No matter how much they miss him, they do not miss, she died long before her body did.