on cloud nine
extremely happy
cost an arm and a leg
very expensive
hit the books
study hard
spill the beans
reveal a secret
in hot water
in trouble
Break a Leg
Good luck
bite the bullet
do something difficult
Under the weather
Feel sick
the ball is in your court
it's your decision
when pigs fly
impossible
raining cats and dogs
raining heavily
get cold feet
become nervous
a piece of cake
very easy