I recently rescued a 4 year old Black Lab/German Shepherd. He's such a perfect dog, very polite and sweet. The only problem I have with him is that he's very nervous and submissive. For example, when I call him, his ears go down and his tail goes in between his legs(still wagging), though he still always comes. I have had him for about a month and a half now, and he has come a little ways in gaining confidence around me. He is dominant and playful with most dogs as well. I'd love to see him with his ears and tail up when I call him! How can I achieve that?