bitter pill to swallow

Example: “Being cut from the team in the final week was a bitter pill to swallow.”

Origin: The bitterness was not incidental. The active ingredients of pre-modern medicine were genuinely and often violently bitter — aloes, wormwood, gentian, and the cinchona bark that yields quinine — and bitterness was so reliably associated with potency that it came to be read as evidence a remedy was working, with a pleasant-tasting preparation regarded with suspicion. Patients therefore swallowed something they knew would be unpleasant precisely because the unpleasantness seemed to guarantee the benefit. That is the exact structure the idiom preserves: a bitter pill is not merely disagreeable but disagreeable in a way bound up with being necessary, which is why the phrase implies acceptance rather than mere complaint. Figurative use is established in English from the 1500s.