It is soooo hard to leave them. When I first got Murphy I would put him in his x-pen. He would bark and cry. This lasted about 2 weeks. When he learned I would come back, he was fine. I always give him some treats before I leave. Leaving him becomes a treat. My first Yorkie would sit by the cabinet I kept the treats. Somedays it would feel like he wanted me to hurry up and leave so he could get his treats.
Then,he would go lay on the couch. They do adjust to your routine.
Other suggestion- I have a web-cam. When I started leaving him I would use my computer to check on him. It gave me the piece of mind that he was not crying or barking all day. Now, I only plug it in when Murphy is not feeling well.
Good Luck!