A dime a dozen
Something common
Go back to the drawing board
Start over
The ball is in your court
It's your decision
Saving for a rainy day
Saving money for later
Spill the beans
Give away a secret
Bite the bullet
To get something over with because it is inevitable
Wrap your head around something
Understand something complicated
Bite off more than you can chew
Take on a project that you cannot finish
Don't cry over spilt milk
There's no reason to complain about something that can't be fixed
Give someone the cold shoulder
Ignore someone
Cutting corners
Doing something poorly in order to save time or money
We'll cross that bridge when we come to it
Let's not talk about that problem right now
Barking up the wrong tree
To be mistaken, to be looking for solutions in the wrong place
Go on a wild goose chase
To do something pointless
You can't have your cake and eat it too
You can't have everything
A penny for your thoughts
Tell me what you're thinking
A perfect storm
the worst possible situation
On thin ice
On probation. If you make another mistake, there will be trouble
Take a rain check
Postpone a plan
The whole nine yards
Everything, all the way.
Do something at the drop of a hat
Do something without having planned beforehand
Let the cat out of the bag
Give away a secret
Play devil's advocate
To argue the opposite, just for the sake of argument
The elephant in the room
The big issue, the problem people are avoiding
Take it with a grain of salt
Don’t take it too seriously