Well... um... that's not very professional, is it? Remember that you're not just being marked on your emotional involvement - the focus is the technical ability and stylistic interpretation. If you're so into a piece that you're crying over it, you're not paying enough attention to your performance.
Remember as well, this is an exam, not a concert! They just want to see how well you can play. As a singer and actor I know the words are important, but so is posture, diction, support, breathing, legato, intonation... there are just too many things to think about to get involved in one aspect of the piece.