花园的墙应该足够高以将世界挡在外面，但又足够低以让天空进来。
The walls of a garden should be high enough to keep the world out, but low enough to let the sky in.
My stomach is a knot of sorrow and anger, but I keep smiling.
Mathematics is not about numbers, equations, computations, or algorithms: it is about understanding.
The only limit to our realization of tomorrow is our doubts of today.
The first prerequisite of a sound foreign policy is a clear understanding of one's own values.