Grief is a human emotion for which there is too little evolutionary biological research. We sometimes indulge in the luxury of thinking that we are the only species that grieves, although that isn't true. Other primates grieve, and so do highly complex social creatures like dogs.

Perhaps, when you understand better the basis for your grief, your brain will no longer experience a compulsion to repeat the thoughts. You might still have the memories, but they will be detatched from the emotion.

Here's a place to start https://medium.com/storygarden/why-do-we-grieve-56f5e8b77cd7