Hello Lonely Girl
Overthinking is a common action and as you say it's hard to get your mind to behave. Do you know what it is that makes you anxious? Psychologist's action or words? Waiting to see her? Your feelings about yourself? Belief that you are not worthy? Something different?
It can be confusing and upsetting. I used to pace while I waited to see the psychiatrist and it didn't help that he was always late even for his first appointment of the day which was mine. I found I got some relief for these thoughts by doing something that needed my concentration. Reading and TV did not work very well for me while a friend of mine used to read novels to get away from herself so to speak. Horse for courses. I embroider which needs me to be in that space if I do not want to make mistakes. But having a physical task was also beneficial.
Have you tried journalling? It gives a time and place to have those thoughts but more controllable as you can go away to do something else if it gets overwhelming. My GP told me to set a time to think these things. It was a specific time and for a specific duration. Set an alarm to tell you when to stop. Once every couple of days. Get it all out then move on. I must admit I was a bit sceptical until tried it. Not always successful but it helped to stop those random thoughts poking their nose in. "I've spoken to you today so you must go away until I am ready to chat again".
Have you heard of neuroplasticity? You can reconfigure your brain despite those who say your brain is hard wired and cannot change. Ask Dr Google. There are some good websites on this topic. Just be careful they come from reputable sources. Making new pathways can help stop the same old same old and certainly help you to push the thoughts aside. Perhaps it would be a good topic to discuss with your psychologist?
Keep talking to us.