Don't get too upset. It may seem like you're not making any progress just because of the repetitiveness of practicing a piece over and over. You also be turning it into a downward spiral by letting your lack of progress invade your focus. If you sit down to practice it with the mindset that "this piece sucks, and I'm not getting any better" then your mind will drag you down. Then since you played it bad, it fuels your mind to keep feeding you negative vibes about the piece. A vicious cycle.Here's a suggestion. Don't play the piece for a week, or even two weeks. Just give it a rest. After some time off, you may appraoch the piece with a new perspective. Sometimes we burn ourselves out with a piece if it's practiced constantly.Also, a great man once said (I forget who it was), "When it seems like you're not making any progress, that's when you are on the verge of a breakthrough."
I think I should relearn some grade 5 pieces so that I feel like a pro at them, maybe that's some reverse psychology to have a new take on the harder stuff (or easy stuff as Bernhard would say....easy vs impossible)