I'm new to the guitar, but I've been playing the piano since I was 4, so this is sort of something I relate to pretty well. I would learn to play the piece I'm working on first. I'm never satisfied til I get it right, but what I do for boredom is to have a set of books, not just one, they work together to develop particular skills. That way, I'm not just playing the same song over and over. If you don't have a set, I'd learn two consecutive songs, no more than three, and divide my practice time among those. Learn those songs til I have them just right. Never settle for less than perfect, and don't be in a hurry to be able to play something harder. Master each step, one step at a time.