“Take a leaf out of someone’s book”

“Catch your breath”

To rest until you can breathe normally again.

“Cool as a cucumber”

Very calm, especially under pressure.

“Come clean”

To tell the truth about something.

“Change your tune”

To change your opinion or attitude.

“Cut and dried”

Already decided and not likely to change.

“Dead in the water”

Unable to continue or succeed.

“Cry wolf”

To ask for help when there is no real danger, so people stop believing you.

“Crash course”

A short and intensive course.