Or, as others said, learn something outside of technology. Learn how to play an instrument, or how to write fiction, or how to paint, or how to ballroom dance (if your health permits).
None of my business, but out of curiosity: What kind of illness gives you that long a recuperation time?
Personally I would probably sit down and learn the core of javascript, getting as deep as possible working toward a better understanding of what's going on under the hood. This is because in my daily work I really just scratch the surface superficially using it to write programs. I would want to understand it to the point where I could start to write something like Node.js from scratch (right now I don't even know where I would begin with this).
The reason for this is because I know C this way, so every time I write a line of code in C, I instinctively visualize what's going on under the hood.
I would like to be able to visualize this same thing with js.
(I have studied formal languages a little bit... enough to know the basics of finite automata, context-free grammars, lexers, etc.)