英语 idioms ¦ You can't have your cake and eat it too

Paul taught me this sentence yesterday: "You can't have your cake and eat it too". It's easy to understand. You have a cake and you have it. However, when you're eating it, you still have it for a while. After you finish  it, it's gone.  For example:

Paul: Haha!

Jason: Come on, I just wanted to ask a serious question, not a joke.

Paul: You can't have your cake and eat it too.

When you get marry, you can use this sentence to describe the freedom.