I'm a big fan of author Andrew Matthews' book, Being a Happy Teen. He recently posted an article on his website about how telling yourself NOT to do something doesn't work. This is because our brain works in pictures, so when you say to yourself, "don't have an accident," your brain pictures you having an accident. Instead, we should tell ourselves what to do. For example, "drive safely." Another example of this principle is to try telling yourself "do not think about kangaroos." Of course, you are thinking about kangaroos! You can read the full article here. I certainly wasn't taught this at school but I'm going to put it into practice this week and see what happens.