Found some articles on Lifehacker:
http://lifehacker.com/think-of-life-as-a-video-game-to-make-the-most-of-your-1516652671

I think there was a 1 url limit / post, so the rest as followup.

The first one was about career choice and timing, the second one is more about daily choices:
http://lifehacker.com/5975824/gamify-your-life-a-guide-to-incentivizing-everything

And here's one practical application to keep track of daily scores:
http://www.chorewars.com/