Yes, I know being friends with someone who wants to divorce you is difficult. I think what helped me was to try and pull my ego out of the situation and be thankful for the good things. In spite of difficult times, there were good years. I have two great kids! Overall, even though it wasn't a perfect marriage, I felt it was good. I appreciated my H for that... in spite of him wanting to leave me.
Also, if this is a person I really love and care about felt they weren't happy with me, why would I even want them to stay? I wanted my husband to be happy. I eventually came to accept that he needed to go out and find it. Somehow, this gave me peace with the situation. It helped me let go and detach. (Although I always believed real happiness would be with me and the kids... anything else would be mirage).
There is no arriving, ever. It is all a continual becoming.