It’s important that your characters grow during the course of your story. Whatever their reactions are in the beginning, it should be somewhat different by the end. No one wants to read about someone too incompetent to learn from their mistakes. It doesn’t win compassion, it breeds frustration.
If in reading your story you realize that your character hasn’t changed, check what sort of situations you’ve put them through. Your character will only grow up if they get whammied both emotionally and physically.
This brings me to external and internal stimuli. My editor told me that my story focused too much on the internal, thus taking my readers on a long-winded, emotional roller-coaster. She said this would create dislike for my main character, and me, which was not my goal. My editor recommended inserting a more exciting subplot and also getting rid of the ooey-gooey friendships.
Conflict breeds growth, that’s all it comes down to. If your characters get along, what’s there to read about? And if the only problem is in their minds, well … unless you’re just awesome it probably won’t end up being much of a story.
Good luck and good typing.