If any living organisms making up us humans suddenly decide they don’t want to function anymore, or they want to be part of a fish as a matter of will, well, they can’t. They can die relative to the body, according to the nature of their elements but they are not equipped with the faculties (far as we know) to think and to decide if they want a better life somewhere else. The path has been made for them. As humans, arguably the cumulation of the same evolutionary forces, we have that ability and we are conscious of the power of it to some degree. Whether we use it deliberately well enough is another matter. I just think, far as this afternoon Zzz goes, it is the most precious thing indeed.