A Bitter Pill to Swallow noun phrase informal
You can use "hard" instead of "bitter" without changing the meaning.
Someone is forced to accept something unpleasant or endure an unwanted fact.
Being defeated by a new player was really a bitter pill to swallow .
I expressed my feelings to her but she said I wasn't her type. It was really a bitter pill to swallow.
It was a hard pill for Harry to swallow when his ex-girlfriend married his best friend.
To refuse to tolerate or accept something unfortunate, or unjust without resistance, argument, or action
Said when someone accepts a bad situation because that's the way things are
The phrase "pill to swallow" dates back to the 1600s. In the 1700s, Rapin Thoyras, who wrote about the history of France and Italy, added the word "bitter" to the phrase:
This event, which happened the 7th of September, N.S. was immediately follow’d by the relieving of time after, with the total expulsion of the French out of all Italy; a bitter pill to swallow.
Since then, people have referred to an uncomfortable set of facts as “a bitter pill to swallow” or “a hard pill to swallow.” (Source: writingexplained.org)