If you believe that karma exists you give it power that way. If you stop believing in karma then it stops existing. You create your world to a great extent with your beliefs or should I say expectations. To a certain extent that is. Thoughts
Our beliefs do not actually alter anything but ourselves. Sometimes attitudes/moods draw you towards certain results, but your on-going fickle conviction with karma does not/will not create and re-create "karma" for the rest of us nor for the world. I think there are far too many people struggling on the other side of the world for karma to truly exist.