Ok, so you realize that you have been living a fantasy, believing a fantasy. The man, woman, child, parent, boss, friend, whoever, you loved is not the person you fantasized them to be. They are human and fallable like the rest of us, and you are heartbroken that this person will not save you and fill you utterly. This person cannot make you whole and will hurt you, because that is what humans do. Sometimes we hurt each other. This is the painful part of fantasy-- it isn't real!
Here is the wonderful side-- just as no one can fill you, no one can destroy you. We have no power over when and if people will leave our lives, but that is ok, because when they go, they do not take a part of us with them. Perhaps as children we had to believe that we wielded some magical power or seduction that kept people in our lives, because abandonment to a child can mean possible death. The good news is that no one can "abandon" an adult. You can simply come and go from my life, but I am no longer abandoned, because I care for myself. If you leave, I will not die. It is painful to realize that the person I invested so much in is incapable of fulfilling me, yet it is freeing to know that when you don't fulfill me, I survive anyway. I don't need you to fill me! My survival is not dependent upon whether or not you love me! This is the wonderful part of fantasy-- it isn't real.