Thanks for mentioning the Kubler/R bereavement cycle. I have often felt that estrangement is like a bereavement. A bereavement without the healing that comes with the healing passage of time. I want to add for Aka at this point, that I am so sorry for the loss you spoke of. I acknowledge that loss is very different to the loss of the relationship you thought you had with an adult child, who may live close geographically, but is on the other side of the world emotionally.
The loss of an adult child as described in this thread, and the COOTL threads, is a different kind of loss. There are none of the recognised social structures or rituals, to help you contain and begin the long process of coming to terms with your feelings of loss, denial, anger, bewilderment and so on. As others have said here, whilst your adult child still lives, there is always hope of some kind of reconciliation, or resolution, whatever that may be. Constant ruminating on hurts, and developing fantasies of some magic reconciliation or resolution, are not helpful, or healthy. Celebs earlier question about what happiness is was a good one. I will probably wish I'd reflected on that for longer but I do believe that we will be best served by living our lives well, compassionately and with love for those around us. Spending time with positive people, with whom we share stable, supportive and loving relationships is very important (for me anyway). I love walking, and find it meditative and relaxing. I have some hobbies, none of which I excel at, and I love the garden. After my parents died, I took some cuttings, dug up some snowdrops, and put them in my garden. The snowdrops are out now, smiling at me. I have a garden ornament that came from mum's garden, and planted a beautiful, white hellebore next to it. It flowered at Christmas and still looks glorious. I was lucky to have a loving mum and find some consolation in watching the things from her garden appear in mine.