hold your horses: (informal) used to tell sb that they should wait a moment and not be so excited that they take action without thinking about it first.
a dog’s breakfast / dinner:(BrE, informal) a thing that has been done badly
He’s made a real dog’s breakfast of these accounts.
have a whale of a time:(informal)to enjoy yourself very much; to have a very good time.
let the cat out of the bag :to tell a secret carelessly or by mistake
I wanted it to be a surprise, but my sister let the cat out of the bag.
a chicken-and-egg situation: problem, etc.a situation in which it is difficult to tell which one of two things was the cause of the other.
the bee’s knees:(informal) an excellent person or thing:
She thinks she’s the bee’s knees (= she has a very high opinion of herself).
the bird has flown: the wanted person has escaped.
take the bull by the horns :to face a difficult or dangerous situation directly and with courage.