Haven't posted before but have been following your thread and hoping you are ok, there was so much superb advice given and you are clearly getting on well.
I just wanted to say that I have had this happen, although we didn't officially live together we were always in each others space, perhaps too much, he was my best friend. More than that, he was my life, we gigged together, all our friends were each others friends, we had known each other so long it was all private jokes and a security born from years of knowing just one person. One day he came round and said we shouldn't see each other anymore, that morning we had talked about holidays, I fell apart for months, lost so much weight I was skeletal, felt like ending everything, all our friends stayed with him and no one got in touch or helped me. I wasted weekends on crying and drinking, then crying some more. During the week I threw myself into work , did 12 hour days. Forgot everything else. Then thought about buying a house, moving areas, starting a degree course.
The hard work paid off, work offered to pay for a masters and I bought a tiny house with the money I saved from going out all the time! I renovated and discovered a love of gardening, grew veg, restored the house, made some good friends and then met my (now) DH. Love at first sight. Married in three years and a DD arrived a year after that. But the best thing about that 18 months on my own was that I figured out who I was and what I wanted to do with my life, which meant when the right person walked by my desk one day I was in the right place emotionally to change bad habits of a lifetime.
it does get better, honestly it does, but getting angry, getting sad, getting drunk is all 100% normal and healthy and also eventually getting even by having a better life than you would ever have had with them. It did take as a pp said, years not to feel sad when something happened which I knew they would like, even now I sometimes think something is funny when DH doesn't get it and I know my ex would have done. But DH is a different person, he isn't perfect, he doesn't get me in the way my ex did, but we are happy, we are balanced and we are equals in our relationship.
Good luck!