...Itll get worse and worse until I start developing problems that I never had before if I keep missing. I just have to try something else, which I hate because I don't like to "quit" anything but I know that's what I have to do before I get too frustrated.
I touched on this in the "What are you working on thread?" talking about working on the 1a trick ladder. You do have to be careful not to actually ingrain the mistake. I think it's important to make sure you consciously change one aspect of how you're attempting the trick before getting too many reps in. If it's a popular trick, I've found it helps to look at as many different tutorials as possible. Sometimes a certain perspective or accumulation of perspectives can get it to click.
I think working on something to the point of frustration and beyond is highly beneficial, but then as others have said, taking a break and returning later can often be key.
Best advice I've ever received as far as practicing was: "Only practice what is right, don't practice wrong."
Which is basically breaking everything down, and only practice doing it right. If you miss one part, stop the trick and start over, go slow until you get it. Then work up to the speed that you want it to be at.
This was from a guitar teacher I had once, but I think the same principals apply to a yoyo trick.
I agree with everything here except the start over part. Yes stop, but if possible stop to work on the element/section you're missing. Starting from the beginning of the trick (or musical piece) is not an efficient use of time. Isolate the weak parts to bring them up to the level of the rest of the trick (piece), and then practice in larger sections, or as a whole.