It's about being able to identify what you can and what you cannot control, focusing on the can control and just letting the rest occur. This is something I struggle with.
I see things, constantly, that are just rage inducing in terms of how stupid they are and how the problems they cause impact my life negatively. And I can't do anything about them. Yet I still spend time being negative, anxious, or otherwise focusing on them. It doesn't help, the problems still happen, and I spent time ruminating about them.