멘붕 – Mental breakdown

You can express this idea with “멘붕”, which

is a combo of 멘탈 (mental) + 붕괴 (deconstruction or collapse). In Korean, this is more often used to express yourself when your mental status is on the fritz. It’s used in various situations where this is the case. For example, you could say it when at the last minute you realize you have to work on the weekend and you have a huge date that you can’t cancel.