Learning to play the guitar is a combination of mental and motor skill acquisition. And to develop motor skill, repetition is essential... Whenever musicians have trouble executing a passage, they generally tend to blame themselves for not having enough talent. Actually, all that's wrong is they don't know where their fingers are supposed to go... you should learn the piece in your head before you play it. And when you do play it, play it so slow that there's no possibility of making a mistake