Time.

Its interesting how we use the term, "spending time".
We spend it.
Like we spend money.
Some of us are very careful about how we spend out time.  Some of us treat it like we worked hard for it, like it is precious, special. But most of us spend it like there is no tomorrow (quite the opposite actually...we really spend it like we know there will be a tomorrow).  We spend it often not realizing how precious it is until its gone, and all we have left are memories....and more time that we wish we had.
What if we could spend time like money?  What if we could chose what we spent our time on? What if we had to earn time, just like money?  Imagine a world of saving up your time, so you could spend it exactly on what you wanted.  You could save and save till you had enough saved up to spend your time exactly how you wanted, where you wanted...with who you wanted.
I think that would be nice.
It would make time seem more valuable.
I'd be willing to bet that there would be a lot less wasting time, and a lot less taking it for granted.