Natural experiments are a powerful tool for understanding causal relationships in the real world.
不管你是年轻还是年老,我还是会做我自己。
It is better to be tried by twelve than to sit on the bench forever.
Start by doing what's necessary; then do what's possible; and suddenly you are doing the impossible.
从做必要的事情开始;然后做可能的事情;突然间你就在做不可能的事情了。