I used to think this too. But just in the last couple of years, I had an epiphany. I noticed 2 kinds, and my reaction to each was opposite. There is change that was MY idea, which I do ok with. There is change that is foisted upon me (or, not so much my idea). That I do not do at ALL well with.

See, I'd always thought that I was so good with it, because I was thinking of all the "turn the world upside down" changes I'd done. Big stuff, giant moves to places unknown etc and my attitude was, "bring it on!" Change! Yeah!

Then it dawned after the most horrid episode of my life.

My psych had cautioned to be careful before a big move I was going to make. I acknowledged it would impact, but kind of poo-poo'd it. I'd done such things SOOOO many times before, right? Thing was… yes, I had free will. No one MADE me go. But I was DEEPLY conflicted, wanting 2 mutually exclusive things. It was not REALLY my idea. And despite the determined attitude as I headed out with….. all hell started breaking loose before I even got there.

My thinking is kind of like Nightside of Eden said. Brain's wiring is wonky to start. Unpredictable and prone to tilt more easily than the average bear's, regardless of why. Some things that others might consider very stressful don't phase me, but the stupidest "minor" things can totally send it sometimes. Even after decades, I don't know for sure what it will pull. Still, it's been helpful to try to parse out the variations of stress (like above).

The pterodactyl, your situation has some very relatable elements (to the one that brought on the epiphany), so I really feel for you. For me, both situational and medicinal intervention was needed. It didn't come out of nowhere (some have, this didn't), but it didn't really matter. It'd gone seriously tilt, wasn't going to just go away. It can be hard to tell, but go with your gut. Even if it started out situational, if it's latched on and going out of control, you still need to take care of it. Even if it's not a straight up chemical issue, sometimes that adjustment can bring us to where we can deal with it (something like getting someone up enough out of depression to be able to benefit from therapy kind of thing, ya?)