I think these can be called unwanted intusive thoughts and can be linked to anxiety - so that our brain is playing out lots of worse case scenarios in our heads.

Mindfulness has helped me alot separate from this type of thought, sometimes I can get to a place where it is just like an annoyng insect walking about in my head and I take no notice. It is not always easy though - so I think holding on to the fact that these are unwanted thoughts for me is good and so it takes away the need / desire to act on them.