Well... I'm assuming what you are experiencing is not a symptom of schizophrenia. If that's the case, then perhaps the answer here may be psychiatric medications? To my knowledge there is no way to stop, or limit, the things we all have running through our heads all the time... daydreams, thoughts, replays of conversations, etc. (Perhaps other members will have some suggestions.) I also have a lot of this sort of thing going on in my head all the time. In my case, I presume it is related to anxiety. And what I try to do is to simply accept it for what it is & allow it arise & fade as it will. It's a practice that is referred to as "compassionate abiding". Here's a link to a description of the practice:

Relieve Distress By Allowing It: Compassionate Abiding 101 | Mindset: Perspective Is Everything

May it be of benefit.