只为自己活着的人，不值得活在世上。
He is unworthy to live who lives only for himself.
It’s not supposed to be easy. Anyone who finds it easy is stupid.
The best paintings are those that make you forget the painter.
The psychologist must be a meticulous observer.
The only way to achieve the impossible is to believe it is possible.
关系模型基于谓词逻辑和集合论，为数据库管理提供了坚实的数学基础。
译文：去偷窃终究是瞒不过家乡的人，偷吃食物瞒不过舌头和牙齿。赏析：人做坏事迟早都会被大家知道，可以瞒得住一时，不能瞒得住一世。
自然界的所有效应只是少数不变定律的数学结果。