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過去總是存在，只是有時比其他時候更明顯。

I constantly see people rise in life who are not the smartest, sometimes not even the most diligent, but they are learning machines. They go to bed every night a little wiser than they were when they got up and boy does that help, particularly when you have a long run ahead of you.

常想到會悔恨終生，就不能不盡孝心；常想到度日的艱難，就不得不節約費用；常想到人的生命脆弱，就不得不珍惜心神；常想到世態人情，就不得不立志奮發；常想到法網恢恢，疏而不漏，就不能讓自己胡作非為；常想到生命易失，就不得不忍氣耐性。

數學中的每個問題都是一個等待解決的謎題，而樂趣就在于解決的過程。

人類心智形成和操縱符號的能力使我們區別于其他動物。