- Edited
Well, it's interesting that you mentioned a race car driver though - because of all people, a racer can't afford to fumble at all. He fumbles, he dies. So although I agree with what you're saying (we need to push ourselves to go a little faster than our comfort zone), it's no use speeding it up to the point of fumbling. I think the trick is to stay just within the "no-fumble" zone until it becomes the "whoa I feel like a tortoise" zone and then crank up the speed a notch. Rinse, repeat
By doing that my current piece is now at the 70bpm "fumble? what the heck is that?", 80bpm "here are my fumble zones" and 100bpm "are these weirdly flailing objects moving in the general direction of the correct keys really my fingers controlled by my brain?" But give it a week or two and I will probably be able to give a different report