It`s not quite in the league of some of these, but I thought I`d share something that happened to me. I have been training at the same club since I was 10 (I am now 25 - though only a green belt because there were long gaps inbetween). I have a sister who is 5 years younger than me and when I was 20 (and she 15 and a couple of belts below me) I would spa with her and always fake punches to her face, telling her to keep her guard up. Later on I got bogged down with university studies and she trained regularly. Then, when I went back, I was sparring with her again and I went to throw a punch, only to be met with a fantastic right hook. I was surpirsed and asked "what happened there?" - Only to be told that I should keep my guard up! Guess it does pay to train regularly.