My husband had this issue, too. The part of his brain that judges likelihood of something happening is overwhelmed by the magnitude of the result if it happens. As long as there's the barest possibility of something happening, to him, it's a done deal.

Right now, he's terrified about what we can do to protect ourselves from WW3. I pointed out that if WW3 were to happen, we'd have much bigger problems to worry about than the disposition of our stock portfolio. Oddly, this reassured him.

I hope you're able to get help for this. It's a horrible way to live.

What helped him was EMDR and meditation. But it took years. And the therapist asking incessantly (to me, at least), "What's true now?" The first few years he'd be so traumatized by potential danger that he'd fall asleep in the therapist's office to escape.