Dude, I wrote the book on being in a rut, e.g. depression. The good news is that is doesn't last. The first step is to just do something. Don't set any goals at the start, except to get out and ride. What I leaned is that you have to take baby steps at first. Especially after a health related setback.

BTW, the flu can set you back a month before you're fully recovered. It depends on how well you take care of yourself. The important thing is to give it time, rest, and take your supplements.