Well-developed characters like to wander all over the place. They'll tell you about your Aunt Edna, that experience with the pudding and a ladder, they'll even tell you about that time when they lost their tooth in the first grade and the Tooth Fairy forgot to show up and how it traumatized them for life.
Experience writers know how to give the characters just enough rope so they can tell an interesting story, but not so much that they end up hanging themselves. Or, at least that's the theory. Because sometimes a character will come across a situation he or she simply can't handle. It's one thing if you've got someone who shouldn't be able to adapt to the situation and it's early enough in the book where this character would need some help. It's another thing altogether if the character is supposed to have some sort of training and sits there like a bump on a log doing nothing.
When this happens, I'll have an interview with the character right then and there. Chances are he or she isn't as competent as I thought or fear has knocked all sense out of his or her head. Either way, I find out what the hell is going on and try to figure out a solution to the problem. If it's early enough in the story, I'll drop in someone who can help. If it's later on? That idiot is going to die and there's nothing I can do to stop it from happening.
Not that I really want it to.