Decide upon your major definite purpose in life and then organize all your activities around it.

I don't sing because I'm happy; I'm happy because I sing.

The higher we soar，the smaller we appear to those who cannot fly.

The most difficult thing in painting is to be simple.

Liberty cannot be preserved without a general knowledge among the people.

经济学是对人类日常生活事务的研究。

数学的本质不是使简单的事情复杂化，而是使复杂的事情简单化。