I know this thread is old, but I just had to add one of my experiences. There was a new girl at my dojo and it was her first day of sparring. I was supposed to explain to her about sparring and be her sparring partner. So I was giving all these tips and saying don't worry sparring is fun. Well we were in our stances and getting ready to spar when I rolled my ankle and I accidentally fell down before I even started to spar. Luckily no body else saw me but her. Also one time a yellow belt in my class went up to a "new" person and was giving him tips in karate. He (the yellow belt) also corrected the "new" person's stances. At the end of class, sensei introduced us to his old instructor...surprise it was the "new" student. You should of seen the look on the yellow belts face.