You can use this idiom when you are very sure of a statement you are making.

To risk everything you have on an investment, a bet, etc.

Used to say when you think something is very unlikely. For example...

A: I'm sure Simon got up really early today and has been working all day.

B:_______! You know very well that he was out partying all night.

Used instead of yes to emphasize that somebody has guessed something correctly.

We use this idiom if a particular event happens then your current forecast, and whatever
you had planned or expected, etc. will no longer apply.