used to tell someone that what they want is impossible

"I'd like to take next week off." "Forget it, we're way too busy." “我下周想休一周的假。”“不可能，我们现在太忙了。”

used to tell someone that something is not important and not to worry about it

"I'm so sorry about that cup." "Oh, forget it - I've got plenty." “那个杯子的事我很抱歉。”“噢，不必在意，我还有很多。”