> Don't allow yourself to make mistakes. Take the challenging section, come up with a drill for just that section, and work that section until it is perfect at the same tempo where you can play the rest of the piece.
Work that section until it is perfect implies that when you start it's not perfect, i.e. mistakes are made. You can't just be perfect with everything all of the time. How would you even know where to start such as to "make no mistakes"? Finding perfection is the process I tried to describe above, you aim to play perfectly and get as close as possible. Nevertheless, errors are inevitable. Embrace their necessity for they are the stuff of learning.
> One drill is to play that scale run forwards and backwards, slowly, concentrating on perfect intonation, even timing, and percussive finger landings.
Reiterating, doing 50 reps of the above is bound to have some errors. You notice them, your brain notices them. If you only ever played things that you can currently do perfectly, or said differently, vacant of any mistakes, how would you ever get better or play new things which are bound to have things you can't already perfectly do?
I think what I failed to portray is that yes, don't "allow yourself to make mistakes." Care about trying to be perfect. You'll still make mistakes and that's a good thing. As you constantly improve and take on more and more challenging tasks, you're also baking in countless reps that are strengthening the "right" networks in the brain and pruning out the ones that aren't right.
I recommend checking out the podcast because I'm definitely not doing a good job of replicating his lessons / sharing of what the latest in neuroscientific literature shows.