No, it makes sense to me. Sometimes I also feel like doing nothing >__< There are times when energy is simply drained and there's nothing you can do against that. Perhaps it's the weather, or who knows what reason.

And it doesn't matter if they don't get it. Do you get it yourself? That's enough.
Anyways, if you'd rather be doing other things and still, you keep going to classes, you're not doing anything wrong o.o