Why they don't move on

He does not move on because I answer. Every time he calls I do. Now he is trying to destroy my reputation at work. Yet if he calls I can only pray I have the strength not to answer. I have been in other relationships since we divorce and I always come back. Why? I'm smarter than that. I have a wonderful life. I'm loved. And still I answer. I'm so upset at myself. It is so contrary to self preservation. I don't get it..