Sounds pretty normal to me. It's easy for the little things to make us fly off the handle. If you felt attacked by the teacher, it makes sense that you got upset about it. Try and let it go and remember that you can't go back and change it. Why let it affect the whole rest of your day? I'm a firm believe that we can "restart" the day at any time by changing our attitude and saying forget that, I'm gonna have a good day because I want to be happy. Try not to worry that you're strange because you're happy one minute and depressed the next. Life is a roller coaster, we can chose to let go of the bar, throw our arms in the air and enjoy it, or let it make us sick.