If I have my health I can carry on. There will be a point when I do quit but I have absolutely no idea when that is.
It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change.
I've often wished when I started a book I knew what was going to happen. I talked to writers who write 80-page outlines, and I'm just in awe of that.