You're too old to be given a job. That's a bitter pill to swallow.

你年龄太大，不能给你工作了。那样的事情是吞苦果。

《柯林斯英汉双解大词典》

It is worth noting that climate change is not a bitter pill only for the poor to swallow.

值得注意的是，气候变化不是仅有穷人才会面临的严酷现实。

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In this example, Catherine is the one who must swallow a bitter pill.

在这个例子中，凯瑟琳就是这个必须吞下苦果的人。

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For industrialists paying reluctantly to clean up their act, that must be a bitter pill.

ECONOMIST: Emissions

In contrast, social is a patience game, which for many can be a bitter pill.

FORBES: Why Small Businesses Are Losing On Social Media

Her prescription is to "fess up" and take the bitter pill that is cost evaluation.

FORBES: Magazine Article