be thankful (或 grateful) for small mercies

be relieved that an unpleasant situation is alleviated by minor advantages

庆幸不利情况已略有改善

have mercy on (或 upon)

show compassion or forgiveness to

宽恕；对…有怜悯之心

may the Lord have mercy on her soul.

愿主宽恕她的灵魂。

leave someone/thing to the mercy of

expose someone or something to a situation of probable danger or harm

听任…由（可能有危险或危害的形势）摆布

the forest is left to the mercy of the loggers.

森林任凭伐木工随意砍伐。

throw oneself on someone's mercy

intentionally place oneself in someone's hands in the expectation that they will behave mercifully towards one

特意恳求（某人）宽恕

at the mercy of

Without any protection against; helpless before

任由…摆布；在…面前无助

drifting in an open boat, at the mercy of the elements.

在一敞篷船中漂泊，任由暴风雨摆布