Keep your chin up and i hope you break a leg! it only happens once in a blue moon. what does this idiomatic phrase actually mean? 1. look upwards and keep smiling. it only happens once every month. 2. stay positive and i wish you good luck! it hardly ever happens. 3. stop talking and i hope you have lots of fun! it only happens once every year. 4. don’t stare at the ground, i wish you would fall over! it happens all the time.