a writes:

I suspect many of the rated pilots here have experienced what I have:
vertigo as bad as it gets in a long flight while in the clouds.

Maybe, although I've read that a great deal of IFR flight actually takes place
in IMC, so even rated pilots might not get that much experience flying through
clouds. Flying through clouds has other hazards besides a lack of visibility.

JFK Jr is a well known example
of someone who could not unlink primal fear from primal but incorrect
action.

JFK had issues, apparently.