Or they didn't split according to a procedure you demanded, or whatever reason. But again you are unhappy because your expectations or demands were not lived up to. Now your unhappiness does not punish your ex, it punishes you. Give up on the programming that people should live up to your expectations. I am unhappy because I fear the future, it is so uncertain.
All futures are uncertain.
Learn to live in the now. You only have to learn to make each day a great day one day at a time. Fear is ignorance - anxiety is fearing the future. When you get goals and know what you are working towards in your life, then you know where you are going. More on your new life.