end of the world

A very big deal or problem. Often used in the negative to describe a situation that one believes is being exaggerated. I know you're upset that you failed a test, but really, it's not the end of the world! You might think that not getting your driver's license today is the end of the world, but it's not. In five years, you won't even remember this day! Would you guys calm down? Yes, we lost out on that account, but it's not the end of the world.