My 5 months old golden retriever is relatively well behaved, knows and answers his commands.. except when we have guests in the house. Then, he jumps at them and totally ignores us. He tends to jump on us too, and even though my husband makes him sit when he does, it doesn't seem to be very efficient. Any idea of what to do about it? I'm so sick of listening to people saying he has bad manners when he's usually pretty good about it!