He who is not contented with what he has，would not be contented with what he would like to have.

战略就是做出选择、权衡取舍；就是要有意识地选择与众不同。

只要心意不放纵，就不会出现差错；只要用心不怠惰疏忽，就没有不能坚守的、随意放纵的志向。

The PAC learning framework provides a formal way to quantify the learnability of a concept class.

量子力学中存在一些我们仍然无法理解的深刻奥秘。