Sometimes in life, you don't always feel strong, but that doesn't mean you're not.

The greatest obstacle to being heroic is the doubt whether one may not be going to prove one's self a fool; the truest heroism is to resist the doubt; and the profoundest wisdom, to know when it ought to be resisted, and when it be obeyed.

形式系统的发展彻底改变了我们对数学的理解。