“A bitter pill” or “A bitter pill to swallow” (similar to 不得不忍受的苦事)
What it means:
A situation or information that is unpleasant but must be accepted.
No one likes to take medicine, but to do the right thing for yourself, you will take it anyway, even though it tastes bad. So this idiom is used for situations where you must accept a difficult thing.
Some key words in this idiom are ‘bitter’ & ‘pill’-
Bitter (辛酸的?) can mean to have a sharp and difficult taste or smell, it also can mean a painful or unpleasant thing to accept.
A pill (药丸) can be used to give you medicine
Usage of the idiom:
Reducing the salary of the employees is a bitter pill to swallow for the company to survive.
Losing to the younger team was a bitter pill for us.