做好事如同背负重物而登山，志向虽已确立，但总是担心力不从心；干坏事如同骑马下山，虽然未加鞭，但却欲驻足而难以自禁。

I think that the most important thing for a director is to have a clear vision of what he wants to do.

The essence of mathematics lies in its freedom.