I have a couple of students who started recently, and teaching them has me focused on fundamentals even more than I usually am. I often say "All I'm going to do is teach you to walk and to breath." Having new students reminds me that this is very true. We are working on fundamentals of posture, how to move, when to inhale and exhale.
Practice seems to focus on the simplest, most common activities. Lately we're spending a lot of time working on breathing in a sensible way for what we are doing, standing and moving properly. Practice is like that, even when I'm working on the "advanced" stuff. Practicing the advanced stuff mostly seems to consist of making sure I'm breathing properly, standing in a relaxed, stable manner, and moving well from my hips without messing up my breathing or my posture. Practice is always practice.
Iaido and Jodo are both kata based arts. The number of kata is very limited. You learn the basic patterns and then you continue practicing them. After a few years you've "learned" all the kata in the system. That is to say, you've learned the pattern of movements that make up the kata. But learning the kata isn't what practice is all about. Practice is doing the kata, studying it, learning to apply those basic concepts of proper breathing and posture to make the movements stronger, more solid, more unstoppable. Every time I do a kata I see things that can be improved. That's just the stuff I become aware of as I practice the kata. True horror awaits me every time I see a video tape of myself. Then I'm left with a grocery list of things to address.
Practice is going about the business of addressing those issues. It's about never being satisfied with where you are, but always trying to move yourself forward. There is always something to practice. Breathing seems like such a simple thing. Even babies do it, right? But breathing properly and fully is difficult. I think I've gotten pretty good at breathing properly and fully, at least when I'm not moving. The trick I'm working on now is breathing properly, fully, and at the right moment for each movement. It's amazing how easy it is to get engrossed in the action of a kata and forget to breath until it's over. I'm still practicing breathing.
And as for walking, I don't have nearly enough time to talk about practicing walking. That's really complicated. I keep practicing it though.