I must study politics and war that my sons may have liberty to study mathematics and philosophy.

善于学习的人，能够透彻地知道事情的道理；善于实践的人，能够把事情疑难之处弄清楚。

From time to time you may stumble， fall， you will for sure， count on this， no doubt， you will have questions and you will have doubts about your path. But I know this， if you’re willing to listen to， be guided by， that still small voice that is the G.P.S. within yourself， to find out what makes you come alive， you will be more than okay. You will be happy， you will be successful， and you will make a difference in the world.

世界是一本书，不旅行的人只读了一页。