You can say it also like this: "The grass is always greener at the other side !"
Or why people are not (or never) happy with what they get/have ...
... it's just a "game", not vital !
On 7th of february 2015 : I start a new adventure in the Divinity world of Original Sin, it's a Fantastic Freaking Fabulous Funny ... it's my All Time Favorite One !