“She just wants to have her cake and eat it too.”　「彼女はケーキを取っておきたいけど食べちゃいたい。」

誕生日にきれいなデコレーションケーキを頂いたら、飾っておきたい！と思うかもしれません。でもやっぱりケーキなので、食べたいですね。でも両方はできません。ケーキを食べたら飾れないし、飾るなら食べられません。このフレーズを使って、同時にはできないけれど、どっちも捨てがたい気持ちを表現できます。

If you get a beautifully decorated cake for your birthday, you might want to keep it and display it in your house. But you also want to eat it. It’s a cake, after all! But you cannot do both. If you eat your cake, you can’t keep it to display. We can use this phrase to describe someone who wants two things that are impossible to have at the same time.