As we get older in life, we realize it's not the cars, houses, money, but other things that are more important...

You see these all the time, and I saw this posted on Facebook recently. I think it's more like this:

As we get older, we manage to check things off the list like acquiring car, houses, money, and the other things in life that we need to live life comfortably. So once we're comfortable because we've acquired those things, we realize that we have other priorities too like family, friends, peace of mind.

To test this hypothesis, take away the house, cash, and car from someone who's 50 years old so their situation is just like the typical person coming out of college. 

My guess: Most people will quickly realize how important that car, cash, and home are for their personal happiness.

Moral: You don't realize how important something is, until it's taken away from you. And that doesn't just apply to people and relationships.