^ This. It's the idea of not knowing and fully appreciating what you have until its gone. When we have x, we assume that it will be in our possession for a long time, whether it be a proper shelter or even a good education. We never speculate the fact that it might be taken away from us at any moment because we don't usually have the need to. But then once we lose it, we realize just how much it meant to us and realize that, yeah, we were taking things for granted.
It's one of the reasons why post-apocalyptic movies/books, like The Road, are so well received, because it shows us upfront the consequences of what its like to literally have everything you had taken away from you, and what people would do to get even a shoddy version of what it was that they had, like a torn jacket or canned food. It tells people in a straightforward manner to not take things for granted.
But, it's all human nature. Each person has his or her own reaction to it.