Suppose you are now 18 years old. Every weekend, you spend about 200 yuan on drinks, meals, taxis, and miscellaneous things. That’s 800 yuan a month. Looking ahead to age 65, if you keep spending like this from 18 to 65—that adds up to roughly 450,000 yuan. Does that sound like a lot? Not really. But that’s the problem. This money could have a completely different story. The key isn’t how big the number is, but the opportunity cost behind every expense you make. Every yuan is making a choice.