I feel like Sx 4s are emotional vampires in that they can successfully get who they want but slowly start to suck the life out of them,always demanding more and more even when the person has given them all they can offer. They make the person feel inferior or hurt them in a way if they can't get everything they want from them and project their fantasies on them in a harsh manner. They react by anger when their needs aren't fulfilled and rather than feel the pain, they project this anger and discontentment on their partners.