After watching this introductory class, I am strongly considering purchasing all of the classes. My 11 month old puppy is pretty well trained, but he is showing leash aggression. I walk him every day and we have really well behaved neighbor dogs. Some of them Barney likes, but some of them he wants to rip to pieces. He's 42 pounds and getting so strong that I'm having trouble controlling him when he meets other dogs. How do I calm him down?