I have been made aware that my face changes when I am involved in doing a technique, either as uke or nage. It is neither a grimace nor a snarl. My face just goes blank, deadly blank. I cannot keep it from happening nor can I do it on call. I have never been able to see it in a mirror. The people in class kid about it; the newbies are frightened by it. One of our nicest instructors has it, too. Any ideas or suggestions?