Now here is the key point: Painful emotions are as much as part of human nature as the law of gravity is part of physical nature.

这是关键点：,人类本性的痛苦情绪,一如物理世界的万有引力定律。

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So，the point is,every object falling under gravity is given by the same formula, but there are many, many objects that can have many histories, all falling under gravity, and what's different from one object and the other object is, when was it dropped, from what height, and with what initial speed.

关键是,每一个受重力作用下落的物体,都有同样的表达式,但是各个受重力作用下落的物体,都有不同的初始条件,所以它们的区别在于,下落时刻,下落高度和初始速度

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