Natural experiments are a powerful tool for understanding causal relationships in the real world.

人不是生下来就懂得道理的，谁能没有疑惑？

当爱成为命令时，恨就能成为快乐。

You have to be willing to make mistakes; the big thing is to not make the same mistake over and over again.

变得更幸福既需要意愿也需要正确的方法。

The more one loves, the less one judges.