Just did the "door exercise" (as seen in the video below) with Seamus, my 10 month old Miniature Schnauzer. Only problem, HE ATTACKS THE LEASH. NON-STOP. I don't know what to do with him. We were able to do the exercise for a while. I told him to sit, and then to stay (clicking and treating accordingly), and when he obeyed I let him go out. But he just yanks on the leash and refuses to listen. He jumps up and gnaws on it, and I know I'm not supposed to yell at him, pull the leash, or get physical with him, but that puts me in quite a predicament. Anyone have any advice for what to do? The "door exercise" starts at 3:24.