I've been making a concerted effort to practice regularly and improve my guitar playing, which had gotten really stuck in a rut over many years. I've concentrated on picking out melodies. I'm amazed at the technique mentioned of leaving it for a few days and then when you try the piece again you find it has improved. Many times I've gotten frustrated and tired of a piece, left it and then been surprised that next time I picked up the guitar I could play it. It's as if it somehow "sinks in" during the down time.