Regret and heartache

I've been ending a relationship for over a year now. The above cartoon is how we were dealing with each others feelings. Both of us too afraid to love and be loved. Always turning to bad habits to deal with life. Me and my anger pushing him away. Him and his alcoholism pushing me away. The two of us never really knowing each other, only knowing each others sick mask. I wanted to grow. I wanted him to grow with me. But he wasn't ready and I wasn't willing to wait any longer. So I forced change as best I could. I was so busy forcing that I squandered away what time we had together instead of accepting him and enjoying him. All the while becoming more resentful and distant. He only wanted what I wanted. To be understood. To be himself. To be loved and to love. But he wanted those things while drinking. And being selfish. And always putting me last. And never reaching my expectations. And robbing me of myself.
I find it incredible that love and hate are so closely related. Such passion is felt with both. I loved him until I hated him. I loved the thought of him. I loved what I thought he could be. When it was good, I loved the way he made me feel. When it was bad, I hated him for what he turned me into to. At times, I hated to be with him. And now I miss him.
I've been mourning the loss of a relationship for a year and a half without having lost it. Without moving on. And now that it's done, I was hoping there would be a sense of relief. Like as if I have been ill for a long time and am now well. But I feel no relief, only regret for things I did or didn't do and a great hollow ache deep within me that swells to tear up my eyes and choke up my throat.
I will be filled with questions of "Did I do the right thing?", "Why didn't I do or say things differently?", "What if I've just made the biggest mistake? What if he only needed more time? What if...".

What if he was my last chance.