Storm in a Teacup

A lot of commotion or fuss about a trivial matter

Don't Judge a Book by Its Cover

Do not judge something by its appearance alone

Cry over Spilt Milk

To be upset about something that has already happened and cannot be changed

Paddle Your Own Canoe

To be independent and self-reliant

Catch Someone with Their Pants Down

To discover someone in an embarrassing situation

Out of the Blue

Unexpectedly, without warning