Having been through this loop a few times myself, the explanation I like best is laid out in Gestalt learning theory (aka the four stages of competence). This tells us that we go through the following steps when learning a skill (caveat: I was told this by a bloke in a pub, and haven't bothered to research it in any depth whatsoever, but I have found it to be true):
1. Unconscious incompetence. You're rubbish at your new skill, but are happily ignorant of the fact.
2. Conscious incompetence. Having banged away at it for a while, you start to appreciate the full depth and width of your ignorance and inability. I vividly remember listening to some Jimi Hendrix after having been going to guitar lessons for a year or so, and being completely blown away by how freakin' GOOD the guy was. Believe me, if you've never tried to play the guitar, you have no idea.
3. Conscious competence. You can do it, but you need to concentrate on it. It's a bit of an effort, but it's all starting to come together.
4. Unconscious competence. Everything's effortless. Doing everything properly is just part of your DNA, you've got to the point where doing it any way other than the simplest, most direct way is just an alien concept that makes no sense. I love to watch people at this level, whether playing instruments, turning wood, building a wall, or whatever, I have complete respect for anyone who's really good at what they do. Especially stuff I've had a go at, and so have some idea of how complicated what they're doing is.
Jeff Atwood recently blogged about the eight levels of programmers, with the Knuths et al of this world sat at the top of his pyramid. And rightly so. But I think there's a lot of mileage in the Gestalt model. I can see my arc of progress through it in a few areas I've dabbled in. I guess the main problem with it is that you can't really judge your own position in it. After all, how do you know when you push on through from unconscious incompetence to conscious incompetence? How do you know that you're fully appreciating how bad you are at
I also have a sneaking feeling that the whole cycle is exactly that, a cycle, where you get to some level of mastery, and then start to realise that, actually, there's a whole new series of levels out there that you were previously unaware of. And at that point, you've just gone back through to conscious incompetence again.
I suspect that programming is a particularly fertile area for this sort of progression. There's a seemingly never-ending progression of bright and shiny new things to play with - say hello design patterns, extreme programming, generic programming, OOP, UML, ....
I know that I'm easily distracted by such baubles. After mainlining on the Gang of Four I spent at least a year in which my code was full of Singletons, Observers, Factorys, etc. None of which improved the code in any meaningful way, and in most cases actively made it harder to maintain for those following in my footsteps (mental note: must send a box of chocs to those poor sods). Which isn't to say that such things don't have a place, just that they should be in my code on merit rather than on a desire to play with some fancy notion I've read about.
Over the last few years my code has become noticeably leaner and simpler, and I think this is a good thing. I've also been working with resource-constrained microcontrollers for the last few years, rather than desktops which to all intents and purposes are infinitely fast and have infinite memory (I know, I know, I'm exaggerating for comic effect, but after you've spent a couple of days trying to save 100 bytes so that you can fit a program in a 4K chip, you get a totally different perspective on things).
I like to think that I passed through one level of unconscious competence (that I now think of as smug complacency) and am now nearing the end of another cycle. Which leaves me wondering where I'll go from here. What will I think of my current self in two years?