Yeah, smart people are just as at risk of self deception as anyone else, and feeling yourself reason things through doesn't guarantee that you're not simply rationalizing.
As you say self deception is easy to fall into. I have on at least one occasion I can remember thought doing something was stupid, and then realized I had done the same thing.
My face still burns from blushing when I think about it.
I don't know which that scenario would fall under, but I know it wasn't pleasant, and it always makes me pause and try to see things from outside my own perspective.