I ask this because I noticed these days on TV, that some actors and actresses while put in even the most hopeless stressful situations, still manage to draw me in on how composed their facial expressions are. If you haven't noticed any examples, then don't worry about it. Maybe it's just me. And it may be because of the director calling the shots, but I'm wondering if its something you keep in the back of your mind when you're filming a scene. Like...imagine falling backwards out of your chair. If you know it's going to happen, I think we can manage our facial expression to hide the comical goofy look of terror that overcomes us. But if we don't know its going to happen, you can't hide it.