正该来时，先生（老子）应时来到这世间；正该去时，先生顺时离开这世间。安于时势，顺应自然规律，哀乐就不能进入心中。

释义：善于用兵的人，会顺应天地的规律，与之同行。这句话强调用兵之道在于顺应自然。

"One way of looking at speech is to say that it is a constant stratagem to cover nakedness."

The walls of the educational system must come down. Education should not be a privilege, so the children of those who have money can study.

水产养殖的效率不仅仅关乎利润——而是以更少的影响做更多的事。