The men who become paranoid or bitter about dating women after dating a horrible woman may have given a lot of themselves to those relationships.
These were women that they may have put a lot of their trust in. That trust was betrayed in some fashion by the horrible woman and the men become paranoid and bitter.
People respond to a sense of betrayal in different ways.
In essence, you haven’t actually allowed yourself to understand that the relationship is actually over.
As long as you still believe that the relationship isn’t really over and there is a chance that you will get back together with your ex, it will be very difficult for you to move on from your ex.