This might seem like a strange question. I've read a lot of books about deliberate practice and the history of music pedagogy, and I'm still a bit puzzled by this:
How do I get more consistent?
For example: On the guitar when my thumb needs to hop up, say, two strings, I often miss the string I'm trying to play. Let's say, for argument's sake, that I miss it 5% of the time. I can physically do the thing, but whether I'm playing fast or slow, I miss just enough that I'm a sloppy player. Repeating this action over and over does not seem to help because I'm just repeating an action which is wrong 5% of the time.
I would very much appreciate advice or leads on this. I have been playing for 20 years, and I'm starting to wonder what my fundamental problem is.
Wanted to add some more here, to clarify: I don't want to get hung up on the specific example I'm using here. I'm more wanting to have an approach to combat the sloppiness which comes for inconsistency.
It will show up even in boiled-down exercises I'm doing for the purpose of trying to get more consistent. It is particularly frustrating when I'm doing a basic exercise like plucking open strings with index and middle and asking my thumb to hop over a string or two. This could just be an exercise where my other fingers are plucking strings that they almost cannot miss, because they are hovering over them the whole time, but my thumb is hopping between two or three strings. The thumb misses enough that it's sloppy, even if I play slowly. The thumb thing is just an example. It could be a chord shape or something else, but the example with the thumb is just such a distilled example of what I'm talking about. Even if I practice slowly, I still miss a bunch, and I am aware that I'm practicing missing a bunch. Maybe the answer is I have to look at my fingers for a while and then wean myself off? (Presuming you can't miss while you're watching your hands.) Sigh.