Let the cat out of the bag
Give away a secret
On thin ice
On probation. If you make another mistake, there will be trouble.
Saving for a rainy day
Saving money for later
Spill the beans
Give away a secret
Take a rain check
Postpone a plan
The ball is in your court
It's your decision
The best thing since sliced bread
A really good invention
There are other fish in the sea
It's OK to miss this opportunity. Others will arise.
You can't judge a book by its cover
This person or thing may look bad, but it's good inside
