The best way to avoid mistakes is to gain experience.

The key to performance is elegance, not battalions of special cases.

You are never too old to set another goal or to dream a new dream.

No arts； no letters； no society； and which is worst of all， continual fear and danger of violent death； and the life of man， solitary， poor， nasty， brutish， and short.

Doubt is not a pleasant condition， but certainty is an absurd one.

学习是系统中产生的任何变化，这些变化或多或少会永久性地改变其适应环境的能力。