解释：想要变得坚强，必定守住柔的一面；想要变得强大，一定保住弱的一面。

Rule of 7 in research. You can find out anything if you are willing to go seven levels. If the first source you ask doesn’t know， ask them who you should ask next， and so on down the line. If you are willing to go to the 7th source， you’ll almost always get your answer.

"if you think tough men are dangerous, wait until you see what weak men are capable of.