This is a really important lesson to internalize (the first one).

In order to change peoples' minds, they have to want to see that they're wrong. I think certain personality types are innately more disposed to the sort of introspection necessary to evaluate one's beliefs and throw out what's wrong.

Really it comes down to how much you care about truth. Coming from the hard sciences, it's surprising how far you can get in this world without caring even a tiny little bit about truth in many fields, most of which involve "people" and not "things": politics, sales, marketing.