have your cake and eat it一块蛋糕你不会吃两次的，如果吃了两次，不就表示可以同时拥有吗。所以，这个习语的意思是“二者兼得、鱼与熊掌兼得”。

【例句】
You can't have your cake and eat it - if you want more local services, you can't expect to pay less tax.
你不能二者兼得——想获得更多的地方服务就不能指望少付税金。

You want to get a pay raise and reduce your work hours? I'm sorry, but you can't have your cake and eat it too!
你想要加薪又想要减少工作时数？很抱歉，鱼与熊掌不可兼得！