The grass is always greener on the other side of the hill.
这山看着那山高。
The grass is always greener on the other side of the hill. 本义是：山丘另一侧的草一直绿一些，那样它的引申意义也就是大家汉语里常说的一句谚语：这山看着那山高，比喻对现在的工作或环境不认可，老觉得别的工作、别的环境更好。因此，当美国人说The grass is always greener on the other side of the hill.时，他/她要表达的意思就是People never feel satisfied with what they've already got., Man is always dissatisfied with his present condition.。
情景对话：
Terry: Hi, Ben, I intend to give up this dead-end job and seek a promising one.
泰瑞：嗨，本，我计划舍弃这份没出路的工作，探寻一份更有前途的。
Benjamin: The grass is always greener on the other side of the hill. Tomorrow is promised to nobody. You'd better think twice before you act.
本杰明：这山看着那山高，哪个也不可以保证明天会如何。你最好三思而后行。