Gary Chynne  uses his skills with the longbow to explain and demonstrate the fundamentals of  mastery by having and following the process in “Guy Language.”
How good can you get?

At 3:10 into this video,  he summarizes his lesson: ” So how good can you get? If you know all your steps- you take your front step, your back step. Get your head, get your bow at 45 degrees, get it back to your anchor, relax your arm. If you can follow those steps and get bulls-eyes, THEN DO IT!
“Do not short draw. Do not overdraw. Do not draw to the right of your anchor. Do not draw to the left of your anchor. Don’t let your bow waver around. Don’t let it wiggle. If its supposed to be 45, make it 45. 
“That’s how you’re going to hit the target. So its just a matter- once you know how to shoot- how good can you get- at taking the steps to shoot properly?”
Probably the best advice you’ll ever get about machining as well. Follow the process. Be true to the process. Don’t take shortcuts or deviate from your known process.
His follow up is TRUTH as well
Anyhow, it’s kind of a blast, and its kind of a bit harder than you would wish, sometimes. Anyhow, when you do that stuff, you start to hit the target.”
Or, as one of the commenter’s posted:
Don’t just practice until you can get it right. Practice until you never get it wrong.
I think that this is probably some of the best machinist advice I’ve run across. What about you?