Well, there's no way to just "stop" anxiety and depression. It's a serious mental illness that can change the way you think. If someone thinks they are suffering from anxiety or depression it's important for them to reach out before matters get worse. If you don't feel comfortable talking to your parent you could talk to a friend or a school guidance counselor. Certain coping mechanisms can help you to calm down in a certain situation, talk therapy, and exercise are all good ways you can help yourself.