How do I turn Photo Memories off?

I keep getting pop ups showing me Photo Memories. The last few have been of my recently deceased wife and the home we built together which I was forced to sell. I don't know why Apple thinks a) this is appropriate or b) why the algorithm 'thinks' these are the best photos in my collection - they are not.

It is crass, insensitive and only serves to remind me of my loss. I am trying to build a new life and although I am making progress this ******* app keeps reminding me that life is just ****.

How can I turn it off?