The past is always with us, and it's always more complicated than we think.
两个物体的相互作用力总是大小相等,方向相反,同时出现或消失且作用于同一直线上。
Strive for excellence, not mediocrity.
解释:向善就好像攀登山峰一样难,向恶就好像山石坍塌那样容易。