As I understand it, your mind is withdrawing from and avoiding the stressor. It's a (maladaptive) coping/protective mechanism.

Aren't they all?

We've all heard of the fight or flight reflex. What isn't as generally well known is that anxiety can trigger a fight, flight or FREEZE reaction.

I tend to do the last one. It's so bad at times I don't even get the normal physical symptoms -- which is a huge problem with regard to the standard diagnostic tests. But I experience agonizing internal suffering and then shut down.

Or you could be getting triggered and overwhelmed by your emotions ... so your mind tries to shut it out.

In any event, in the absence of more effective responses, it's your psyche doing it's poor best to protect yourself the only way it knows how.