To try to do something you cannot succeed in.
A day late and a dollar short.
To become a fan of something already very popular.
Jump on the bandwagon.
To fail or be defeated.
Bite the dust.
A concise explanation.
In a nutshell.
Reveal a secret you were supposed to keep
Let the cat out of the bag
Someone new to a job.
Tenderfoot/Dude
It is your turn to make the decision.
The ball is in your court.
To go to bed.
Hit the hay.
Being overly excited or angry.
Going bananas.
Accomplish two tasks in a single action
Kill two birds with one stone
Admitting you were lying.
Acknowledge the corn.
The whole nine yards.
To decide between two bad options.
Caught between a rock and a hard place.
Two peas in a pod.
Do not assume you'll succeed.
Don't count your chickens before they hatch.
When you feel the consequences of your bad actions.
Chickens coming home to roost.
To do a great job.
Knock it out of the park.
Something that rarely happens.
Once in a blue moon.
Being calm under pressure.
Cool as a cucumber.
Heavy rain or downpour.
Raining cats and dogs.
Talking like your are impressive when you are not.
All hat and no cowboy/All hat and no cattle.
To focus on something that can easily be messed up.
Keeping your eye on the ball.
To do something without worrying about the consequences.
Throw caution to the wind.
Describing someone very important to you.
The apple of my eye.
A gift should not be judged.