Catastrophising can actually help!

What's the worst that can happen? What can I do to mitigate it?

If there's nothing one can do then it's genuinely anxiety inducing... so your anxiety is appropriate.

If there is something that can mitigate it, do it, and know that you've done it!

When you catch yourself going into a negative loop, stop yourself and think of or write down the absolute worst possible scenario (and really, how bad is this, likely minor, negative thing in the grand scheme of things?), the most likely scenario which happens most of the time, and the best possible scenario (how good could it be, similar to the bad outcomes?). What separates those possible outcomes? Chance? Effort on your part? Other people?

If it’s effort on your part, it gives you actionable steps you can take and that’s great for anxiety, everything else being out of your control should actually help as well, though, especially when you intentionally step back and look for the most likely event.

I always have this sense when I’m driving home from an overnight elsewhere that my house will have burned down or my animals will be dead or something. I know it’s absurd, but more than that, even if that was the case, there’s nothing I could actually do about it, and I know one of my neighbors would call the fire department and text me if my house caught fire. So when I have that intrusive thought I stop myself and take a step back - logically it’s very unlikely it will burn down when I’m not home because I spend 99% of my time at home - if it is going to burn, it is likely going to burn when I’m here, and I literally never worry about that. So why do I worry about the rare occurrence?

It doesn’t help immediately, because you didn’t logic yourself into that worry, but eventually you can train yourself to be a bit more realistic which, while it may not fix the intrusive thoughts, does help a ton with breaking the rumination cycle.