I tooootally understand this. I have a 'spend one hour every day learning something' (unrelated to schoolwork or other certification-driven studies) which I've been doing for years, and it means that even if a day seems like it was useless, I always know I still spent that hour learning something.
...as far as the Challenge is concerned, I think I'm done writing music for now: I have like four new songs which I still barely know, and I'd rather practice and memorize them than write more. I really really want to get back to my book, but it'll all be rewriting and editing, so I don't know what word counts will turn out like, but it might get me back onto the challenge.
Edit: Sick! That explains a lot about this weekend. Ugh. Not productive. Tired. Mleh. Hopefully will improve in next few days, finally get to hardcore editing of Another Turn of the Wheel.