I think that when you are anxious that your mind needs something to do so it ruminates. Going over and over something is sort of like OCD. Understanding how you became anxious is really important IMO. I believe that people become anxious because of instability or uncertainty while growing up. Our nervous systems are developing while growing up and they need calm and secure experiences in order to imprint and learn calmness. I think that we have plasticity, so we can undevelop and redevelop (rewire) at any time. There is also some genetics to this.