Under the weather
To feel very very happy
To feel sick or sad
Crack someone up
To make someone laugh
To make someone cry
Gut feeling
A bad intuition
A good intuition
Piece of cake
Something difficult to do
Something that is easy
Hit the books
To not read books
To study
Once in a blue moon
To never happen
To happen rarely
When pigs fly
Activity that never happens
Activity that always happens
Go the extra mile
To make an effort
To not do anything
Bite more that you can chew
To do many activities
To be lazy
Raining cats and dogs
Go to sleep
A heavy rain
Hit the hay
To wake up early
Go to sleep
Back to square one
Start again
To do something perfectly