Puppies are babies. They will do things that make you mad, just because they are learning. And as they grow up they act just like teenagers. They try to get away with doing what they want, instead of what you want. And adult dogs often were not properly taught, they need help learning. Being firm is OK getting angry is useless, and can make things worse. Teaching them in a way that makes them healthy and happy, instead of afraid or angry, takes patience and understanding.