魚與熊掌不可兼得 [ㄩˊ ㄩˇ ㄒㄩㄥˊ ㄓㄤˇ ㄅㄨˋ ㄎㄜˇ ㄐㄧㄢ ㄉㄜˊ; yu2 yu3 xiong2 zhang3 bu4 ke3 jian1 de2]
 lit. the fish and the bear's paw, you can't have both at the same time (idiom, from Mencius); fig. you must choose one or the other
 you can't always get everything you want
 you can't have your cake and eat it

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