It's almost a biological law: kids will kill the relationship that produced them.

这几乎是一个生物学定律：孩子们会扼杀产生他们的关系。

And it goes both ways, our heart's capacity for love obeys the biological law: Use it or lose it.

它是双向的，我们内心的爱的能力服从生物学法则：使用它或失去它。