That’s really what I’ve found fluoxetine to be helpful for stopping thoughts from persisting. I still get negative thoughts, but then move onto another thought, rather than the negatives becoming a loop.
In terms of worries that have played on my mind over the years, not one of the scenarios that I have created in my head has, in hindsight, been something that has ended up happening!
I’m saying this not because I think fluoxetine is a route to take, but because I think your book will be helpful as it deals with a similar issue by an alternative method. It’s important for your well-being, I think, to take back some control in a situation where you feel everything is beyond your control.