hold your horses
wait a moment
cost an arm and a leg
very expensive
call it a day
stop working on something
break a leg
good luck
a dime a dozen
Something very common
Hit the sack
Go to sleep
On the ball
Doing a good job / aware of any changes or developments and quick to react to them
Miss the boat
It's too late
pull someone's leg
to tell someone something that is not true, as a joke
Under the weather
Sick
A perfect storm
the worst possible situation
Give someone the cold shoulder
Ignore someone
It's a piece of cake.
It's easy
It's raining cats and dogs.
It's raining hard
Let the cat out of the bag
Give away a secret
Once in a blue moon
Rarely
