I am not at all good at hiding my feelings. (I am also a very poor liar. Probably not a coincidence.) If I'm bored, I will look bored, no matter how hard I try not to. If I'm pissed off, everyone knows. And apparently, if I'm feeling uncomfortable in front of students, even if I try to hide it, at least some of them are able to pick up on this rather easily.
So the upside of this, I guess, is that you'll always know where you stand with me!