Life lessons will be presented to you in the order they are needed. Everything you need to master the lesson is within you. Once you have truly learned a lesson， you will be presented with the next one. If you are alive， that means you still have lessons to learn.

有趣的是，有时候我们记得最少的人却给我们留下了最深刻的印象。

安全困境是国际政治的一个基本特征，因为国家增加自身安全的努力往往会降低其他国家的安全。