What is the origin of the idiom "a bitter pill to swallow" and when to use it?

The idiom "a bitter pill to swallow" is used to describe a situation, piece of information, or decision that is difficult to accept or come to terms with because it is unpleasant, disappointing, or hard to bear. The origin of this idiom lies in the idea that taking medicine in the form of a bitter-tasting pill can be an unpleasant experience. Therefore, this phrase draws from the idea of comparing the difficulty of accepting an unpleasant reality to the distasteful experience of swallowing a bitter pill.