I am learning a piece right now that has a series of jumps from low notes to high notes, and it is really fast. I have been working on it for about two weeks now and I have been breaking down the part, learning it in chunks, and then slowly piecing it together. For a while it was coming along great, but one day last week when I went to play it, I failed epically. And ever since then it has sounded awful. I am extremely frustrated and I feel like just skipping this piece and moving on from it. My teacher said I should just keep working on it because after a period of it sounding really bad, it will all of a sudden sound so much better. I am finding this very hard to believe since no matter how many times I play it, I feel like it keeps getting worse. Any suggestions on how I can fix this and not feel so frustrated all the time when I practice?