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