Back in college, when I studied theater & acting, an important lesson was taught by the instructors - how to react on stage as if you were in the moment, without anticipating the lines of your fellow actors. If you showed anticipation in waiting for the lines, or showed your emotion too early, then the acting was unauthentic and not believable by the audience. The same came be said for writing a novel. If your characters always anticipate what's coming next and are ready to handle every situation, then there's no drama and no believability. Readers will stop reading. Characters need to be thrown curve balls, they need to be sideswiped, and their reactions need to be true. How would a real person react to a similiar situation?
I was reading a story today, and was in awe of how the writer built in some really great moments of authentic interaction between characters. It made me totally buy-in to the story and to the characters, and from the first pages I knew I'd be hooked. I trusted the writer and somehow knew she would continue to surprise me with more moments - authentic, believable moments.
So throw your characters under the bus once in awhile, and see how they'll react. It might just make for a great twist in your story, one that will hook readers to keep reading.