你不能因为某件事困难就放弃。

He said that the way of the world is to bloom and to flower and die but in the affairs of men there is no waning and the noon of his expression signals the onset of night. His spirit is exhausted at the peak of its achievement. His meridian is at once his darkening and the evening of his day.

真正的数学家始终是学生，永远在学习。

The right of a nation to kill a tyrant in case of necessity can never be doubted.

You’ll get 10x better results by elevating good behavior rather than punishing bad behavior， especially in children and animals.