Nerves can certainly make mine worse. I’d say a lot of the problem is concentrating on many steps at once. If I’m doing drills that are quite predictable I might do a decent job, but when I don’t know what’s coming the technique goes out the window. I have very slow processing speed. I’ve done enough practice that I am certain it isn’t enough to make things second nature.
I did only recently read that the antidepressant I’m on, which I plan on going off in April, can cause problems with motor coordination. Perhaps switching to a new medication might have some effect.