If that’s what’s happening, that would be a really weird way of looking at things!
Meaning, if you’re continually improving by a little bit here and there, a few bpm more, a little smoother, better hand synchronization, and so on — well that’s not “failure” to me! If I see any sort of improvement day to day, I know I’m on the right track. Hell, incremental improvement is realistically the only kind that’s possible in most situations.
Taking the kinds of things I work on as an example, learning new hand movements with every possible grip, anchor point, guitar body, and so on, in no way do I actually expect to get there completely with each combination before moving to the next. That would be crazy. I don’t even know how half of them are even supposed to work! I just know they do and I have to figure out how. On some days I’m better on electric with one grip, one movement and muting. On other days I’m better on acoustic with a different grip, different movement, and no muting. Even if none of them are really working right yet.
But again, if I am seeing any sort of improvement from one day to the next, one week to the next, in any aspect, then I call that success. Given the sheer number of things I generally try to work on, and the number and complexity of the unknowns, I can’t see any other way of doing this. But I think everyone is in the same boat when it comes to learning something as complicated as guitar, whether or not we realize it or acknowledge it.
Guitar motor learning is, almost by definition given the number of variables, “interleaved”!