How to lose interest in someone/something?

I decided to end my friendship with someone a month ago but my feelings are all over the place about it. Part of me feels like it was the right thing to do as the friendship was practically dead. Part of me still wants to reach out, and part of me feels like this is just part of the healing process. I’ve done models on this but it still feels like my feelings are all over the place.

I also want to apply this to things like losing interest in food.

If there are additional resources in scholars that can help please let me know.