An opinion repeated among friends has not necessarily been tested outside its welcome.

Agreement among people who like you feels like confirmation and is nothing of the sort. A view can be stated fifty times at the same table, refined, sharpened, met with nodding, and still never meet anybody with a reason to disagree. What all that repetition produces is fluency rather than evidence. You get better at saying it, which is easy to mistake for its becoming more true.

Take one view you hold confidently and find the strongest version of the objection to it. Reading someone who disagrees carefully, rather than someone mocking them, is the cheapest test available.