A Blessing In Disguise:
Something that didn’t seem good/helpful at first, but turned out to be good.
I was sick and went to the doctor. It was a blessing in disguise because I found out I had a heart problem!
A Chip On Your (My/His/Her/Their) Shoulder:
Being angry about something that already happened or about what people think.
The team has a chip on their shoulder because people think the team isn’t very good.
A Drop in the Bucket:
A little bit of something much larger.
I needed $1,000. So when I worked for a month and only saved $50, it was just a drop in the bucket.
A Month of Sundays:
A very long time.
I haven't been to the gym in a month of Sundays.
A Picture’s (picture is) Worth a Thousand Words:
A picture can provide a much greater description than just some words.
When I saw pictures from her vacation, I realized a picture’s worth a thousand words.
A Slap on the Wrist:
A small punishment.
The police officer was kind and just gave me a slap on the wrist.
A Taste Of Your Own Medicine:
You are bad to others, and they do the same back to you.
I guess the bully got a taste of his own medicine when he got punched in the mouth.
When things are done in a legal or proper way.
Don't worry. Everything here is above board so we don't have any problems with the police.
Accident waiting to happen:
Something that will certainly end in disaster.
An electric appliance next to the bathtub is an accident waiting to happen.
Add Fuel To The Fire:
Make a bad situation worse.
He is adding fuel to the fire by telling the whole story.
Against The Clock:
There’s not really enough time to finish what needs to be completed.
We are working against the clock on this project.
All In The Same Boat:
Everyone has the same issues/challenges/problems.
Well, we’re all in the same boat I guess.
At the drop of a hat:
Right away, instantly.