As someone who's been kind of struggling with the catastrophising / worst case scenarios I can say that the megathread over on /r/anxiety has been quite a big help in ways that go above and beyond the war. One fairly big "aha" moment was reading about "reassurance seeking" and how it's probably the worst thing you can possibly do for anxiety. It's where you end up hyper focused on scrolling and scrolling through threads and articles looking for reassurance that your worst case scenario won't happen (or often in my case, airing the worst case as a statement in a desperate hope for someone to say "you are being highly irrational but I'm here to care and help and this is why..."). The fact is no one can 100% guarantee anything, but you end up obsessing over trying to find that unachievable 100% reassurance against something with a 1% chance of happening and nothing is ever enough. So it feeds into the anxiety and is a vicious cycle.
Since learning about that a couple of days ago I've tried to avoid reassurance-seeking and it already helped. Definitely something to be conscious of if anyone else is an anxious type.
The other thing is we can end up losing sight of the unlikelihood of most things (I.e. yes the chance of nuclear annihilation is a lot higher than it's been since the Cold War, particularly if he gets desperate, but it's still relatively unlikely due to MAD and multiple people/steps needed for launch) and putting life somewhat on hold out of a concern for something that's unlikely. When the thoughts get to the point mine we're getting to (let's call it "contingency planning") you can end up putting yourself at a LOT more risk from the nearby "contingency" than you were ever at risk for with the scenario at hand.