1. 'A piece of cake.' - This is used to describe a task that is very easy to accomplish. "Repairing this will be a piece of cake." "That language exam was a piece of cake." 2. 'Hit the hay.' or 'Hit the sack.' - This is used merely to say that someone is going to bed or to sleep. "Time to hit the hay, we need to get up early tomorrow." "I'm tired, i'm going to hit the sack." 3. 'Once in a blue moon.' - This is used to describe an event that rarely takes place. "Once in a blue moon I go to Florida and spend a few days on the beach." 4. 'Run out of steam.' - This is used to describe being out of energy, or feeling exhausted. "I can't jog anymore, i'm out of steam." "John looks like he has run out of steam." Have you heard these or any others?