maybe try meditation because it clears the mind and weakens neuron paths in the brain responsible for automatic negative thoughts. I cannot explain it well but I've seen a video about it. I have read about a guy who overcame stuttering thanks to meditation. He would meditate every morning. I have to try it myself. Also, remember to always separate thoughts from you. You are not your thoughts, you are watching it, so it can't be you. Also, you can think positive thoughts all the time on purpose for a period of time so there will be no space for negative thoughts. I know that it is easy to say harder to do but we have to try I guess. all the best