We have the most wonderful 13 month old Alvin, black lab/retriever, who loves to grab an arm, hand etc. when we come downstairs in the morning to greet him, or just affectionately when we return home from somewhere. He has no aggression whatsoever but he does hurt when he gets a hold of us and we worry that he might hurt someone else without meaning to. How can we stop this? Any suggestions would be greatly appreciated. He is currently in the proofing stage of an almost perfect recall so this other problem sorted will make him perfect.