I've always wondered what the limits of mind over matter were. Like if I practiced every day, Could I learn to move my toes individually or with more dexterity? Could I focus on that random muscle that twitches in my leg and get it to stop, or move it myself?
I like to think of things like yoga, meditation, and prayer as a messy abstraction layer for controlling the parts of your body you normally can not. Created over millenniums of black-box reverse engineering by people of different levels of skill and honesty who are not sharing their results. One of the things guided meditation, and hypnotists will do is have you purposely relax each muscle group one at a time. Though for a specific twitch, that really depends on what is causing it.
I wish there was more skeptical, but open minded research into ancient practices. It seems it's all either people who blindly believe in their flavor of magic, or people who go in assuming it's nonsense and miss the step between the action and the result.
To put it more succinctly, mind over matter is enough of an issue that we have double blind studies to account for the placebo effect.