This quote jumped out to me right away for two reasons. First of all, I've seen that this idea is totally true. I'm trying to keep my attitude towards life as a positive one, looking to make a difference with others and there are many times I see the results coming back to me from what life has to offer.
The second reason is that I'm currently listening to one of Earl's audio books on my iPod. So many countless lessons about life, getting better, thinking better, etc. Very uplifting things that I try and listen to a little bit every morning on my way into work. It starts my day off in a great direction. I suggest you look this guy up and get all that you can that he's written and/or recorded.
Try focusing on this a little bit - every day, and watch what happens. Let me know any results that you see... as that can be a great lesson for not only myself but others too.