Today you are going take an exam. As you are heading to the classroom one of your friends texts you on your phone. The text message says "break a leg!" You may wonder "Why would my friend send me a message like that? Why does he wants me to hurt myself?" Of course your friend does not want you to break a leg bone in the classroom. If someone tells you to "Break a leg" it really means good luck!
"I hear you have a big interview for a job with Google today. Break a leg!"
"I know you are giving a speech in front of the whole class today. I just wanted to tell you - break a leg!"
"I heard that you are finally going to ask the girl you like out on a date today. Break a leg!"