Or, why it's not a bad thing if you don't get it right all at once.
Two years ago, I learned my first bo kata, shuji-no-kon. I learned it in a weekend and took notes and videos and have practised it regularly ever since. These last couple of weeks, we have revisited this kata and in just two run-throughs with my sensei, I picked up two major, fundamental flaws in how I was moving and half a dozen smaller things to work on as well.
My initial thoughts were along the lines of - "I wish I had known/realised this ages ago", but my second (and subsequent) thoughts were - "I probably wouldn't have understood beforehand anyway".
I'm seeing this in my empty-hand work too. Improvement seems to happen piecemeal or in sudden jumps, when something that I have seen many times before just suddenly stands up, slaps me on the face and shouts "THIS is how you should be doing it!" And the reason why, I think, is that the brain and body can only focus on so much at once.
When starting to learn something, it is only basic shape (as can be best understood given prior experience and context) that can be taken in. Doing a kata, for instance, the gross movements are what are learned first - usually wrongly or poorly. But I contend it is almost impossible to learn them properly with no prior exposure to them or to the movements or principles they contain. We have to do them poorly to begin with.
Then, when we have become more comfortable or familiar with it, we suddenly can see places where improvement can take place, because we now have a context in which to learn. Actually, more often than not we don't see the places for improvement, but we are now in a receptive head-space to understand and appreciate what is being pointed out to us. It was like that with the bo kata for me. My sensei picked out two things I was doing wrong, and when he pointed them out to me, they resonated with me and made such good sense in the context of what I was trying to do that I couldn't believe I hadn't picked up on them before. In fact, I could see in my minds' eye the video footage I had from my initial exposure to the kata and the very points he was raising were shown there. It was just that until now, I wasn't familiar enough with the context of the kata or general bo-principles to be able to see or appreciate them.
I assume that once I have bedded down these improvements, something else will jump out as a result. I have been having that happen recently in increasing my emphasis on sanchin practise, where all of a sudden pieces of sanseru and seienchin are coming to life because of things I have been improving in sanchin.
So, I guess the moral of the story is, don't expect to learn everything at once, learning never stops, and without stuffing up, you can't get better.