How do your characters react to mistakes, costly or otherwise? Do they try to learn from them or do they try to pretend they never happened? When mistakes do cost them dearly, how do they respond to that? (It's easier to shrug off a simple mistake which doesn't do much harm after all than it is to a mistake that cost financially, endangered someone else and so on).
Were there things your characters could have done to have avoided the mistakes but perhaps their own personality traits got in the way? How do the other characters in your story react to the mistakes and those that made them? Is it a "game changer"?
All things to think about. Of course as readers we want the characters to make mistakes as these will lead to more tensions and drama until the mistakes and other issues in the story are resolved. Are the mistakes in keeping with the type of character you've created?