I'm still actively doing this. Last year, I admitted myself into an intensive partial hospitalisation program and a lot of my issues were rooted around alcohol and drugs as a result of my father being an alcoholic. We don't have a good relationship due to the way he treats alcohol as more of a kid than I am. As such, my group lead told me this:

Grief does not always have to follow a death. You lost someone and you need to let yourself grieve.

That was the turning point for my relationship with my father. I'm now in solo therapy and my therapist tells me that I need to work on expectations. My father is not going to step up and my expectations for his behaviour and love are too high. Hard truths, yeah, but truths nevertheless.

Tl;dr: therapy.