The most obvious signs of a dog being unhappy are lowering its head and drooping tail. When it is angry with its owner, it will avoid the owner and not want to get close to the owner. It is also common for dogs to be unwilling to move, suddenly become irritable and fierce, and have a loss of appetite. Signs of an unhappy dog. In addition, dogs may also be in a bad mood during the season when they are sick or needing to shed their hair. When the dog is unhappy, the owner should coax it more and play with it more.