1) My expectations of the world change when I maintain a positive attitude. I will see the good in things that otherwise would have seemed only very negative to me. I will recognize God at work even in the midst of chaos or tragedy.
2) My attitude will have a positive effect on those around me, bettering their lives and making them have a better attitude when they're around me.
Anyway, I think we all have witnessed the power of positive thinking. Now, it's just a matter of consistently living it out.