Briseis is right, the moment we tell ourselves to stop obsessing about something, we will obsess about it more. It's so unfair, but so true. Think about it. If you tell a group of people not to look at the elephant in the room, the first thing everyone is going to do is want to look at the elephant in the room, right?
The main reason we obsess is UNCERTAINTY. We hate UNCERTAINTY. When something in our life is unclear or uncertain, we will obsess about it until we think we can create some kind of certainty.
The first thing to understand here is that nothing in life is certain. Until we accept this, we will never stop obsessing. What's the old saying, the only thing in life that is certain is death and taxes. So sad, but also true if you think about it.