The cool-o-meter measures the level of coolness in a person.

He keeps a cool head in stressful situations.

He always keeps his cool in stressful situations.

He kept his cool during the argument.

He blows his cool whenever he loses a game.

He had blown his cool and yelled at his boss.

She is keeping her cool despite the stressful situation.

She is blowing her cool after receiving the bad news.

He kept a cool head during the crisis.

He blew his cool when he found out he failed the exam.