I think I am overly sarcastic to my girlfriend, whenever she makes a mistake i have to jump on her and rub it in. I also play jokes and pranks on her. She has been telling me recently that i am being mean but i think i am being fun. I try to watch myself but even subtle humor hurts her feelings. Granted, she has been having a stressful summer with driver's ed and other home issues, but am i really being mean, and how can i better myself?