One common American English idiom is "24/7," which means "all day, everyday." Another common idiom is to say someone has a "short fuse," meaning that person is easily angered.
When one gives another "a taste of his own medicine," it means treating him badly because he treats others badly. The phrase "butterflies in my stomach" is an idiom describing how it feels to be nervous. When one is asked "has the cat got your tongue," it is the same as asking the person why he cannot or does not speak. The phrase "down for the count" is an idiom that means unable to participate. When someone is a "fish out of water," it means that person is uncomfortably out of place.
When one is searching for something and says it is like "finding a needle in a haystack," he means the object is practically impossible to find. If someone says they need to "get something off my chest," it means he has to talk about something that has bothered him for a long time or admit to something he has done wrong. The phrase "let the cat out of the bag" is an idiom that means telling a secret. When one says he "plays second fiddle," it means he is less important than somebody else. The phrase "lose your marbles" is an idiom describing someone who has gone insane.