Some of us, even though we're normally functioning adults in most other ways, will always have a little difficulty with left and right.
Some things your head knows and some things your body knows. That gap can be a hurdle. For those of us with a bit of a dominant right brain, knowledge tends to be processed in a more wordless way. It then has to make a delaying detour to the left brain for "language encoding" when verbal labels are required.
My hunch is that knowing left and right is a left brain function. For me, knowing left and right is a two step process. I must first identify which side of my body "left" or "right" is referring to before I can react to whatever the situation demands. (I remember as a child actually holding on to my left arm to help myself remember which direction was left. It's like my arms knew which direction is which --they just had to let my head know.) I'm one of those people who when I'm being directed in a new activity must be told "now turn right...no, your other right." If I have to take half a beat to identify right and left anyway, being absorbed in a new and/or different activity causes my already busy right-dominant brain to put those pesky right/left labels to the lowest priority.
This can be illustrated by my having a hard time learning new steps when I took Ballet classes for my PE credits in college. I was able to easily learn the exercises while standing next to the barre--usually you only had to worry about one leg making the majority of the motions.
But when we were out on the floor, both legs (and the rest of the body) were fair game for learning new sequences. That meant not only putting individual movements that I could just barely remember the names of together, but also when we slowed to break down a step, I found myself standing in an unfamiliar (sometimes awkward) position and was then told 'now move your left foot back.' I had no idea--which one is my left?? I'm already feeling like a pretzel in motion, how am I supposed to be keeping track of my left and right on top of that?
Needless to say, it took lots of stumbling practices before my feet learned the steps and they could dance by themselves. And once they did learn the steps it was a magical moment. As my feet learned what to do, the words and labels stopped getting in the way. I thoroughly enjoyed doing the sequences. But my feet and body had to know what to do before my left brain could chime in with reminders for technique.
So for some of us, knowing left and right is of low importance--a necessary nuisance. I'm not denying that these terms come in handy. It's just that for me in this vast world of left brained-labeled items, there's a hole where the right brain has taken over and refuses to let these labels "left" and "right" stick.
I hope I'm not the only Sunday Scribbler who's had trouble with left and right.