Fish is what I want; bear paws are also what I want. You can't have both fish and bear's paws. You want to take the bear's paws but give up the fish.
You are what I want; the country is what I want. You cannot have both. Which one should you take and which one should you give up?
Because a person falls in love with a city. Since you have given up on me, I will never see Chang'an again.