It's good to have the bad days ahead of time. Then you can learn how to handle them. Probably everyone is going to tell you the same thing, just try to calm down and remember you are doing this for fun. Try to treat it as just another class to learn from, which you will no matter how well you do. Dogs are human, they have good and bad days too, just go with the flow, try to relax and do the best you can for the dogs. Have fun, really, try to have fun.