I've gone through that. Every waking moment thinking of stuttering or avoiding people so I won't have an opportunity to stutter. Unfortunately the answer is as you said, stop thinking about it and stop making it into a negative thought feedback loop. It has to end. You can't end it abruptly but you can make small positive steps everyday to not be so hard on yourself and try to clear that anticipatory feeling of oncoming stuttering. It's not easy I know