I asked this myself. From what was told to me, it's changing my lens of perspective. I had trouble with writing a letter to my brother that passed (it was an assignment of mine from my T). I got stuck on forgiveness and apology and what it entails with the living (like how could I apologize and forgive a person that passed away?).

Some people write in a journal of conversation to the deceased love one, others write letters and at some point it's supposed to bring a different type of closure. I'm still working on this myself, so I don't really have an answer of what works. But it's worth a shot?