Having a reflex to think about a question fast enough compared to the reflex to rationalize can cause someone to not notice their arguments for some answer, then say they never rationalize, or just not rationalize.

I have had periods in my life where I would have been convinced I was thinking absolutely clearly, but in retrospect it was blitheringly obvious that I was rationalising like hell.

People's subjective reports turn out to be unreliable, news at 11.