I lost my dad a couple years ago. At first I was in shock more than anything. I had seen him go down hill over a couple years in nursing home, so I should not have been shocked but I was.
For me I had to reinvent who I thought I was. I had to let go of things I hoped for or expected that then I knew would not happen. I guess it was coming to terms with all the positives in my life of that relationship.
Support groups helped because others validated how I felt with grief and sadness and emptiness. Everyone grieves in their own way but having people to help us cope can be a great addition.
This article speaks to some of what I was going through
Coping with the End of a Relationship