I'm afraid I've made a whole bunch of mistakes with my Great Pyrenees puppy and need some advice about how to fix them (if I can). He came to us at only 7 weeks old (mistake #1). We didn't get our sheep until he was 15-weeks-old (mistake #2). I have played fetch and chasing games with him all this time (mistake #3). I didn't establish my dominance with him very well while he was small (mistake #4). Now I have a very lovable but large puppy who is far too big for me to physically handle when he shows undesirable behavior. He tries to chase the sheep whenever I take him into their pasture. He mouths my arm,bites at my clothing, and jumps up on just about everyone. He is showing traits that I have read indicate that he might not have the correct temperament to be a good LGD like having a huge chase instinct ( he loves to play fetch,which is supposed to be very unusual for a Great Pyrenees) and giving the sheep "let's play" body language. Anyway, I am a discouraged and confused as to what to do. I have never had a dog before, much less a livestock guardian, so I am really a fish out of water. I did sooo much reading before we got him, but the reality is totally different. Is it possible to hit the "reset" button with him and start over doing things better? If so, what should I do ?