(I reworded this after reading what you wrote about your wife and her cancer.)
I am sorry that you are going through this,
@bobcat48 ! Unfortunately, we cannot bring them back. It took me a long time to get over my grief and guilt after my husband died. I would repeat in my mind the incidents that happened on the day he died, and I kept trying to see if there was something I could have done better, but it was his time to go. We all must go one day. Some go sooner than others.
I found peace after going to the monastery and speaking to the elder and the nuns. They told me no matter how much I wanted him to stay, it was his time to go. I also spoke with the priest of our church. His words comforted me. It took me 9 months to stop crying daily. It took me 4 years to finally accept what happened and to move on.
Keeping busy helped me cope. I went back to school and got more active in church. Don't stay alone. Become active in your community or do something that keeps your mind occupied. Grief takes a toll, I know. But don't let it overwhelm you. There is so much that life has to offer.
Another thing that helped me was to give donations in memory of my husband. For example, I bought several trees for our library in his memory. Now whenever I see the trees, I think about him.