Oh, there is another thing in there when the impact of the worst thing that can realistically happen is actually worth worrying about - “what steps can I take to keep it from happening (and lower the amount of worrying I do).” This is not one of those cases. This is: I have a weird mole, what’s the worst thing that could happen, I could die of skin cancer, what can I do about it, have my doctor take a look…
This is great advice. What works for me is to come up with a retort to the worst case scenario and then repeat it every time the obsessive thought appears. Then find a distraction.