They do not obsess constantly about the past nor do they worry about the future. Being in the now is your point of power. If you are to communicate successfully with an animal you need to be as focused, attentive and aware as they are. Its a great lesson. When you count your daily blessings make sure you count the animal companions in your life.
All dog behavior is normal to a dog.
Barking, chasing, digging, chewing, and biting are all perfectly natural dog behaviors. In fact they are necessary skills in dog society. However, these behaviors are socially unacceptable to humans. Personally, I strongly disagree with this. When you adopt this approach to training you immediately set up an adversarial relationship based in domination, subjugation and coercion.