I'm sorry Grace
Letting go of a relationship is very difficult, maybe even more so when it's not what we wanted. My AH and I are divorcing after 25 years together. It's incredibly painful... but the right thing for both of us. It wasn't totally my choice. I asked him for a 6 month separation. He said that was not an option for him and staying in the same home was not an option for me; therefore, we are divorcing. I have been working through this al-anon book:
Opening our Hearts, Transforming our Losses. It is helping me deal with my grief. Aside from that, other things that are helping me are: journaling my feelings, keeping a gratitude or blessings journal, doing special things for myself (like treating myself to lunch and a matinee or just spending a weekend day in my jammies watching movies/reading books), and crying. I carry a small package of kleenex at all times because I never know what may trigger crying. I've also been looking at things I could have/should have done differently and why I did them so that it will hopefully help prevent me from making the same mistakes in future relationships.
On the whys, I felt like my AH was handling the impending divorce better than me and also thought it was because maybe he doesn't/didn't love me like he said he did. I realized that is not necessarily the case. Sometimes, even when we love someone, the relationship is not right for us at that time. My AH and I have always said that we bring the worst out in each other. For us, I think it's the ACOA traits we both have, combined with the usual A/codie traits that make our relationship not healthy.
Be easy on yourself, Grace. Give yourself time. I have hope that it will get easier/better for both of us!