Question
Use the paragraph to answer the question.
Cara was nervous. Her class was performing in front of the entire school during lunch! Cara had a solo in one of the songs. She walked past her brother's class on the way into the cafeteria. "Break a leg!" he whispered to her as she walked by. Cara suddenly felt excited instead of nervous.
In one to two sentences, explain the meaning of the idiom used in this paragraph.