I agree with Carrot- don't redo papers because there are so many new ones you could do. What I do though if I actually have no idea how to do a question (not if I get it get it wrong because of a silly or something) is I'll look at the solution and then immediately after cover it up and do the whole question from scratch so I can get that line of thinking into my head.
Also, who is this clown who posted above me? He stole my avatar