By Sydney Smith. This post first appeared on ThreeKookaburras and is used with permission.
When the protagonist has a character flaw that prevents them from getting what they want, the story deepens and becomes more richly layered.This character flaw can be called the internal antagonist. It drives the protagonist to act against their own best interests, while also blinding them to that fact. For example, in Pride and Prejudice, Elizabeth wants more than anything to see her sister Jane married to Mr Bingley. She does everything she can to promote the match, within the limits imposed by the social conventions of the time.

When Mr Bingley (pictured in the BBC production) leaves the neighbourhood, with no prospect of returning in the near future, according to his jealous, conniving sister, Elizabeth sends Jane to London to make every effort to enter the Bingley social circle.
By doing so Jane will meet him again and strengthen their relationship. But Miss Bingley won’t let Jane past the front door. Jane is forced to go back to Longbourn, disappointed.
Elizabeth doesn’t realise, until it’s too late, that the most decisive action she could have taken in furthering the match would have been to be nice to Mr Darcy and get him on her side. But she was blinded by her prejudice against him, and that prevented her from taking such a step.
Mr Darcy is also blinded by his character flaw, or internal antagonist. That is his pride. He finds himself attracted to Elizabeth, but his pride tells him she would be a poor match. Her station in life is inferior to his own; she has no money, no important connections, nothing of a worldly nature that would make a marriage between them advantageous to himself and the Darcy family. He finds he can’t suppress his feelings for her, and at last, he proposes marriage.
But his pride drives him to do it in an insulting way. He talks about her social inferiority, and how rational judgment argued against the match. It’s hardly surprising that she turns him down. He doesn’t realise his pride was preventing him from getting what he wanted, until she told him so. Why on earth would she want to marry a man who, out of pride, had destroyed the relationship between Bingley and Jane? Now each must work to correct their character flaws. Only when they meet each other as equals, emotionally and morally, can they get what they want.
In Jane Austen, just about every character comes with their internal antagonist. Caroline Bingley’s internal antagonist is her jealousy. She wants Darcy for herself, but her jealousy drives her to disparage Elizabeth to him, thus driving him further away. Mrs Bennet’s flaw is her vulgarity. She wants to see Jane married to Mr Bingley, but her vulgarity so offends Darcy, who pulls out all the stops to prevent the match.
Every time a character opens their mouth, out spills their character flaw. One of the differences between the good guys and everyone else in Austen’s fiction is that the good guys are able to recognise their character flaw and correct it. Mrs Bennet remains vulgar to the very end, Miss Bingley remains jealous, Mr Wickham remains a lying psychopath and so on. Only Elizabeth and Darcy have what it takes to change and grow.