My go-to practice for this sort of thing is "compassionate abiding". Here's a link to a description of the practice just in case you're not familiar with it:

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

And then here are links to 3 articles, from PsychCentral's archives, that may be of some help as well:

9 Ways to Let Go of Stuck Thoughts

Sneaky Rumination: Replaying Conversations in My Head

Why Do You Ruminate? And 3 Steps to Stop It