Why fixing your character's worldview isn't enough
Under your protagonist's rule for how to live sits a low opinion of themselves, and an ending that fixes only the rule lands early.
Why your character keeps believing the lie
Your protagonist keeps their false belief because it is paying them something real, and the payout should be good enough that someone in the story admires it.
Your protagonist isn't stupid for believing something false. The belief is paying them.
Your protagonist lives by one false belief. That's what StoryDNA calls The Lie: one sentence your protagonist would defend if you challenged it, like "trust no one" or "perfection earns love."
A belief that only hurt them would have been dropped years ago. The one your protagonist keeps has been working. It's a deal, not stupidity.
If it's "trust no one," the payout might be that nobody has betrayed them since. If it's "perfection earns love," it might be a career people envy.
Without a payout, your reader watches a character make an error and feels superior. With one, your reader stops judging and starts wondering if they'd have made the same trade.
In Jerry Maguire, treating clients as deals has made Jerry rich and respected. The Lie isn't holding him back. It's holding up his whole career.
People rarely keep a belief that hurts them unless it's also giving them something they need.
Write your protagonist's Lie at the top of a page. Under it, write what it has gotten them, and the name of one character who admires what it got them.
When your character's best quality looks like a danger
The Lie makes your protagonist's best quality look like a danger, so the change doesn't add a strength, it points the one they already had somewhere new.