[pessimizer]

I don't think this is completely true, because I'm fairly sure I have an accurate idea about how people feel about me, and am rarely surprised. I do think it is more true for some than others.

Like you, I blame it on the Illusion of Transparency: when we try to guess what other people are thinking about us, we do so with complete awareness of ourselves, so that model we make of other people is unnaturally good at seeing our flaws, especially the ones we're making an effort to conceal. Not only are people generally great at lying (they're not going to see through you), but they're likely also not paying that much attention to you.