The grass is greener on the other side

I've always felt that the human tendency to live life always thinking that the grass is greener on the other side is driven by something fundamental to our existence.

I think of it as a manifestation of entropy into our very being. Because if you think about it, as shown in this Happiness and Cyanide comic, pretty much every human on this planet always wants to pursue something that they don't have or aren't currently experiencing. This urge transcends race, gender, religion, social status, wealth, etc.
It's like a bunch of atoms inside a container that is placed in a vacuum. Those atoms want to break free, spread out, and fill that void - to obtain the highest state of entropy possible.

So maybe that's why we live our lives like this, constantly wanting things and experiences that aren't our own. Once you realize that we are just a collection of self-aware atoms trying to reach the highest state of entropy. You'll realize that we shouldn't be depressed about all this.. it's just our nature, it's the way of the universe, it's the way the arrow of time moves forward.

It's very humbling to know that despite how much we hype up the existence of our species, we are still slaves to very fundamental laws of nature.