The Fatal flaw

In Monica Leonelle's book Novel Writing Prep, she states that a character's fatal flaw:

is a way of looking at the world (could even be a worldview) that will change (or get resolved) by the end of the story.

Similarly, in The Science of Storytelling, Will Storr states that our brains constantly try to process information and make sense of it. Since there's so much information, the brain misses important details and creates a flawed understanding of the world.

The controlled hallucination inside the silent, black vault of our skulls that we experience as reality is warped by faulty information.

In both cases, the false beliefs are true because, until now, it has helped the character make sense of the world. It makes them feel in control.

The trouble comes when that belief is shaken, and the cracks in the beliefs start to show. First, the characters will resist, and then they'll start accepting it.

Piece by piece, brick by brick, the wall of the fatal flaw is weakened and dismantled until the character faces the ultimate question:

Who am I?

Are they the type of person who behaves like this? Believes this? Makes these choices?

This realization allows a story to expose the flaw and question it until the character eventually understands and changes their understanding of the world—hopefully for the better.