Appreciate any comments on mouthing. When I'm playing with my puppy he gets excited and sometimes nips at my hand or arm. I have him enrolled in puppy classes with several other puppys and the trainer said to squeeze his bottom lip over his teeth so he can feel the pain. I say no bite and redirect his attention. When I tried what the trainer said my puppy seems to get angry and lunge at me in a defiant way. I think this may cause aggressive behavior. Any input will be appreciated.