过去总是紧张的，未来是完美的。

"In the study of computational complexity, we often find that the boundaries of what is possible are defined by the limits of our imagination."

想让小孩子在旅行中表现良好，可以准备一袋他们喜欢的糖果，当他/她不乖时，就向窗外扔掉一块糖。