I even learned what sets and reps were!
My biggest issue was to remember not to lock my elbows or my knees. Keep them strong but loose was something that took me a while to master. But master it I did and, almost twenty years later, I still make sure not to lock my elbows or knees if I'm doing any kind of weight bearing activity.
About ten years ago I decided to try yoga. As I slowly learned all the different poses, I also slowly learned how to keep my knees in line with my ankle so as not to hyper-extend. Again, it took a while but I still remember and still make sure that any stretch I do has my hips, knees and ankles lined up properly.
My latest challenge is trying to make my shoulders and hips talk to each other.
It's a swimming thing.
See, when I first started swimming, I developed a very barge-like stroke. I plough through the water in a very inefficient way. Ideally, I should have a lovely body roll that lets the water slip by me and reduces drag. Kinda like this:
I've been working on it and was starting to get the feel for how my shoulders should rotate.
Turns out that my shoulders now rotate very nicely. But my hips don't move a bit. As my coach says "I can watch your bum all the way up and down the pool. It doesn't move".
So my next body position to master is one that is going to involve me learning how to use my core to keep my shoulder and hips moving in sync. I'm sure, like all the other moves, once I get it I'll get it. In the meantime though, it feels really awkward and is rather hard to maintain for any length of time.
Practice, practice baby!