Long, drawn-out farewells can excite your dog and make the isolation more obvious when you're gone. Just when he gets all worked up and ready to play, suddenly you disappear. With all this energy, your dog will either try his best to get you to come back or he will have to vent his energy in some other way. Since he can't build model airplanes or invite his buddies over for a hand of poker, he does doggy things - like chew, dig and bark.
We often think our dog is destructive because he is angry that we left him, but he's really just trying to have some fun since there is nothing else to do. He may be relieved to be able to do those things he normally can't do when you're home. He may be thinking, "Thank goodness the owner is finally leaving! Now I can chase the cat, dig up the tomatoes, get in the trash, and bark at the neighbors. They never let me do those things when they're home."
Some dogs are stressed, nervous and insecure when they are left alone. They express this nervous energy in typical dog fashion - chewing, digging, barking and housesoiling.
Dogs need to feel happy, secure, and comfortable when you're away. It's important to give them things to do while you're gone. Provide them with lots of toys or a digging pit in the yard. Often another companion pet can help alleviate the boredom.
When you are home, set aside scheduled time periods to give your dog undivided attention, play and exercise. A happy, well-exercised dog will usually sleep contentedly during the day while you are gone. Be sure that one of the scheduled play sessions occurs before you must leave for the day. Give your dog a chance to settle down before you leave and don't make a big deal of your departure - just leave without any emotion or commotion.
If your dog is not used to being left alone or already has panic attacks when you leave, then gradually accustom him to your leaving. Practice leaving and returning several times a day until he gets used to your departures and realizes that you are not abandoning him forever. Gradually leave for longer and longer periods of time, but start out by leaving for just 5 minutes and returning again.
Check here for training tips for new puppy owners.