> I’ve had that experience. And losing it — even acknowledging that it was lost

What are you talking about? You don't know how 99% of the systems in your own body work yet they don't confront you similarly. As if this "knowledge" is a switch that can be on or off.

> I gave 42 years to this thing, and the thing changed into something I’m not sure I recognise anymore.

Stop doing it for a paycheck. You'll get your brain back.