I also had a newfie who lasted for 8 wonderful years and I'd be happy to share some insights. Cera (short for Triceratops) usually had sad-looking eyes. Sometimes she smiled though too. I think it's just a trait that they have melancholy appearances, Cera was a happy dog that usually looked like she was on the way to a funeral. She was also very lazy and enjoyed making as much noise as possible when laying down so, I think, everyone would know that she was open to a belly rub. I think she's just sad to see you go, like most dogs. Beware of her sense of humor and her willingness to test her boundaries. Big dogs are smart, manipulative and are very funny. Unfortunately, they also have tragicaly short life-spans and arthritis due to their rapid growth. I'd suggest some glucosomine powder to mix with her food on occasion to promote good joint health and enjoy having the best breed avaliable. It may take time for you two to get used to eachother, but there is no better reward than the friendship of a newfie.