The deepest insights in mathematics often come from the most abstract theories.

筹划洋人的事情一定要先了解洋人的情况，要了解洋人的情况一定知道洋人的情况。

So given a Time Turner, I would tell my 21-year-old self that personal happiness lies in knowing that life is not a check-list of acquisition or achievement. Your qualifications, your CV, are not your life, though you will meet many people of my age and older who confuse the two. Life is difficult, and complicated, and beyond anyone’s total control, and the humility to know that will enable you to survive its vicissitudes.

"The pictures are the first thing. The words come later."

我们不仅要造好车，还要卖好车，更要服务好车。