This is probably an impossible question but I'll ask anyway! As you move through the lessons how do you know when it's time to move on. For example when you learn X or Y and you practice it over and over should you have 100% mastery before progressing or is 90% good enough or 75% or....? It just seems to me that you could end up spending hours and hours perfecting some cord progressions or get reasonably proficient and then move on in the hope that you'll end up doing similar things in the later lessons and improving that way. However the neurotic in me just worries that I'm carrying "issues" with me and they'll eventually catch up and stop me progressing? Any thoughts?