Can't change who you are
A leopard can't change his spots.
Curiosity killed the cat
Being inquisitive can lead to unpleasent situations
Hit the sack
Go to sleep
Sleep like a baby
Have a deep sleep
Important person
A big fish
Study
Hit the books
Be patient
Hold your horses
Raining hard
Raining cats and dogs
Something easy
A piece of cake
Something visual says more than words.
A picture paints a thousand words.
Can't judge a book by its cover
Can't judge something or someone by its appereance
Small part of something
Drop in the bucket
Feel nervous
Butterflies in the stomach
All ears
To listen carefully