Yeah, sometimes I can't concentrate because I have anime opening songs stuck in my head O_o

What I do when that happens is go for a quick walk outside while trying to forget it or play some other music to drown it out.

Also you shouldn't try doing too much of nothing, I'm trying to get out that habit too. So I just do bit by bit (depending on when it's due) and leave it when I know I have enough time to do more later and when I'm sastified or too tired to do more.