Be honest with yourself. Is there someone new in the office who is kicking ass, raising expectations about what is possible from all of you? Or has your work slipped on its own? Are you approaching things with the same passion, or are you taking those good reviews as a sign you can coast? (You can't-perhaps you've heard the phrase, "What have you done for me lately?") Then again, there are bosses who periodically like to pit people against one another, either as a motivational technique or simply for sadistic satisfaction. As a loyal employee, CC hates it. As a boss, damn, that works well.