If you want a programming language, learn one that is far away from what you know. If what you know is dynamically typed, interpreted languages, learn a static typed compiled language. If you work with procedural languages, learn a functional one, and vice versa.

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?