"Practice makes perfect" - typing wpm, music instruments, abacus, driving/riding, sports, knitting and list goes on.
Running on a treadmill or elliptical every day but your weight loss hit a plateau, is probably because of muscle memory.
Returning to an old house where I grew up 25 years later and still able to switch on lights before entering the next room or hallway, even the placement of the switches are far from logical, also thanks to muscle memory.
But what got my attention?
I found a locker combination lock that I used everyday during college years, wow that was 18 years ago. Needless to say I don't remember the combinations but I DO remember writing them down.... somewhere... now only if I can remember where I placed that piece of paper.
Given up finding that paper, I googled "hack combination locks". While watching one of the videos (which proven to be useless later) I was fiddling with the lock, rotating the dial with right hand thumb. All of the sudden *click*, it opened! Yay~!! But... how? Well, at least I have the last number now. For the next 30 minutes or so, I tried and tried but no luck.
So I watched more videos online and played with it more; consciously NOT paying attention to the lock and, of course, click, it opened again. Darn, I still didn't know how I opened it. My thumb must have its own brain.
Repeating this process several times, "pretending" to watch videos and peeping at the thumb frequently (if that makes any sense), finally I saw how it opened that damn lock!! AMAZING MUSCLE MEMORY!
Haha, take that, thumb. You can't hide secrets from me.