Based on many years of martial arts practice and two years of guitar practice I'd also add: - You need to challenge yourself to move the needle. If it's so sl

Based on many years of martial arts practice and two years of guitar practice I'd also add: - You need to challenge yourself to move the needle. If it's so slow that it's too easy you're not accomplishing that. - Sometimes too slow is more difficult. - There are some aspects of training where it doesn't matter if you make errors. E.g. strength or flexibility can be developed while making mistakes and without those you can't actually execute the proper technique anyways. I think the trick is to try to avoid locking in the error by switching to other practices. - Some physical skills are speed sensitive, i.e. the slow doesn't transfer to the fast. - It can help speeding things up to the point where you make mistakes just to get speed up, and then coming back to normal speed. That F barre chord is still driving me crazy though with any technique I try to throw at it ;)