He was cool as a cucumber.

To pour oil in troubled water

You have to be <u><em>a cool customer</em></u> and be patient if you want to get the best buys.

We have to <u><em>keep our fingers crossed</em></u> till the final result is declared.

In double-quick time

You need rest; you look a bit <u><em>run down</em></u>.

To play fast and loose

Get down to brass tacks

He <u><em>went back on</em></u> his promise to vote for me.