Michael Crichton said this quote

“ There's one problem with all psychological knowledge - nobody can apply it to themselves. People can be incredibly astute about the shortcomings of their friends, spouses, children. But they have no insight into themselves at all. The same people who are coldly clear-eyed about the world around them have nothing but fantasies about themselves. Psychological knowledge doesn't work if you look in a mirror. This bizarre fact is, as far as I know, unexplained. ”