I actually disagree with the 'play perfectly' example. It emphasizes the beginning of the practice and de-emphasizes the end. If playing the whole thing 20 times is boring, imagine how boring it is to play the beginning over and over until you get the whole thing perfect 5 times? Guitar hero has a mode that lets you practice pieces of a song. You can practice each segment to perfection, then play the whole song. This…
Another problem with stopping and restarting with every mistake, is you learn to stop and restart when you make a mistake. This makes it really, really awful if you're playing a recital and slip up just a tiny bit (obviously, you should practice it so you don't slip up /at all/, but let's be realistic here. Even people studying to be performance majors make mistakes in their recitals) - your first instinct would be t…
The key is not making mistakes in the first place! Do slow practice on short passages. If you make a mistake then decrease the tempo (or play a shorter passage) until you can play it correctly. Repeat it until you can't do it wrong. Then increase the tempo.