当随机化不可行时，匹配方法可以是一个强大的工具。
"Matching methods can be a powerful tool when randomization is not possible."
优化编译器很像核电站。它们都非常强大，也非常危险。
"The only way to make sense out of change is to plunge into it, move with it, and join the dance."
The passions of men are commonly more potent than their reason.
“小河都知道这个道理：别着急，我们总有一天会到那里的。”
Hold to the now, the here, through which all future plunges to the past.