~었/았어야 했는데 (~eoss/~ass-eo-ya haen-neun-de) – should have done this but… OR it should have been like this…
This grammar expression is translated as above but its use and function usually extend much further.
~었/았어야 했는데 is used to express regret about past events (one should have done this instead of that or it should have been like this instead of that), and we would usually also add what may or may not have happened if those past events had or had not occurred.
If we want to just to express regret, use ~었/았어야 했다 instead.
We can only attach ~었/았어야 했는데 behind action verbs or adjectives (descriptive verbs).
Another thing to note is that you have to be talking about a past event and not something currently happening or in the future.
어제 동물원에 갔을 때 날씨가 좋았어야 했는데 비가 와서 구경을 잘 못 했고 입장비도 낭비되었어.
When we went to the zoo yesterday, the weather should have been good but it rained so we couldn’t tour well and even the entrance fee was wasted.
오늘 아침에 먹은 음식은 다뜻했어야 했는데 늦게 일어나서 차가워졌네.
The food I that I ate during breakfast today should have been warm but I woke up late so it got cold.
배탈이 나서 다뜻한 차를 마셨어야 했는데 왠지 아이스 커피를 마셔버렸어요.
I had an upset stomach so I should have drunk warm tea but somehow I ended up drinking iced coffee.
지난 달부터 공부했어야 했는데 시험이 코 앞에 닥쳐도 공부하지 않어서 잘 못 봤어요.
I should have studied since last month but even when the test was at the eleventh hour, I didn’t study so I did badly.