We are aware that we are expected to always be professional. Curiously, it seems that we're seldom, if ever, expected to act like human beings. We are no different than anyone else; we have "bad days" at work, same as anybody, and sometimes, it can be very difficult to constantly maintain that textbook professionalism that the majority of us strive for. I suggest that you do a Google search for a very brief, but very much on point, piece entitled "Me, The Lousy Cop" and take the few seconds required to read what it says.
Seen on a bumper sticker: "Exercise. Eat right. Take vitamins. Die anyway."