Success is not the key to happiness. Happiness is the key to success. If you love what you are doing, you will be successful.
成功不是幸福的关键。幸福才是成功的关键。如果你热爱你所做的事情，你就会成功。
所有的真理一旦被发现，都很容易理解；关键在于发现它们。
A mathematical proof is a poem written in the language of logic.
数学的本质在于它的自由。
The best time to work on your career is when you're in your 20s.
过去是学习的重要来源，但也是错误的重要来源。