使用，而不要滥用...节制和过度都不会使人快乐。
Use， do not abuse...Neither abstinence nor excess ever renders man happy.
The only limits in life are the ones you set for yourself.
The best way to learn mathematics is to do mathematics.
Every saint has a past, and every sinner has a future.
每一本书都是一个待发现的世界，充满了惊喜和教诲。