Two observations I’ve made about how good people are at things:

People who aren’t good at something talk about how awesome they are at it.

People who are great at something talk about the humiliations and failures that got them good at it.

I’ve found this pattern far more accurate than I would have expected. I love hearing stories from people about the disasters that made them who they are. That’s how I know they’re good at the thing at hand. They’ve gotten over their insecurity through experience and aren’t afraid to share. People who are afraid to share tend not to be so good at the thing — I think because they are afraid of being associated with the failure.
Incidentally, the stories about failures and humiliations are much more entertaining and engaging. They invite you to learn more about the person. The stories of how awesome someone is are more boring and invite you to talk about yourself. You end up trying to one-up each other.
People who know me well would no doubt wonder how I reconcile the above with my consistent noting of how awesome I am. For one thing, with the above observation in mind, I’m actually being humble (no one notices this except me).
But the main way to reconcile it is with another observation everybody has made: you can’t take things too seriously.
There are exceptions to the observation, as well.