To be thankful or grateful for one's good luck usually while avoiding a bad situation
You should count your lucky stars as you managed to avoid that violent car accident.
To punish someone or something harshly
He's a really strict teacher, so he'll definitely lower the boom on you if you don't do your homework.
To be cautious; to plan ahead instead of taking a risk
I like to err on the side of caution and always keep some money in my savings account.
To give someone false information to prevent them from discovering the truth
He cheated on her, yet he threw her off the scent by saying that she had to have mistaken him for someone else.
One's real character is revealed, which stands in contrast to what they have been pretending
My friend's mask slipped when I call upon him in a time of crisis.
Very quickly; in a short period of time
I will do it in no time flat.