I don't know what will work best for you, but personally I sometimes get caught up in a cycle of ruminating thoughts and cannot seem to convince myself not to believe those things despite knowing they are likely untrue. In those cases being mindful of the fact that my thoughts are off and not trying to engage, but maybe choosing to let those thoughts be and distract myself temporarily with something else can sometimes help. It's not a long term solution, but can prevent me from going down a rabbit hole I can't think my way out of. As others mentioned there are therapies that might be useful, so maybe this is a good topic for therapy? When I tried CBT we discussed my cognitive distortions like catastrophizing. While it wasn't that helpful at the time, I do sometimes remind myself of those distortions when worrying about something and it helps me remember I cannot trust everything I think.