It gets better
Stay strong. You know in your heart that you don't want to live with an alcoholic. If you did, you wouldn't have initiated his moving out. And, just because you feel sad, it doesn't mean you aren't correct in your original thinking. I'm in a similiar spot, and perhaps my experience can help...
Last week I decided it was enough. My long-term AB wasn't a horrible person by any means, but living with an active alcoholic just isn't living. I packed a bag and I've been staying at my mom's. I told my AB that we could discuss the future of our relationship after he attended an AA meeting (he has been in and out of AA), and that I would be happy to come home when he was displaying what I consider to be active participation in his sobriety. It has been exactly one week today.
For a few days he drank and didn't call. I got more and more confident in my decision to leave; much like you. Then I had an evening where my mom wasn't around, I didn't have much to do, and he left a message about promising to go to AA. I felt weak and almost nastalgic about our past. But, I decided I was going to stick my ground. Boy am I glad I did. Those lonely, bored, sorrowful feelings passed. I actually felt better after enduring my evening of sadness because I made it through. I didn't burst into flames, time didn't stop, and the sun came up the next morning.
I realized the fear of not being with him was what was causing my sadness. For almost two years I've done EVERYTHING with him in mind, and the reality of removing him from the equation is daunting. Now I do the following when a "sad" moment starts to arise.
1. I try to imagine how I would look at a friend in my situation. I would most definately tell her that she should stop sacrificing her life for an alcoholic who won't seek help.
2. I stay busy.
3. Talk to someone other than him. Anyone but him. This forum, my mom, my dog, anyone.
4. I remember the times he peed on me when he was passed out drunk in bed. (something about being peed on that brings the reality of the situation to the surface)
Like everyone has said; it is okay to mourn the relationship. Hopefully you can get the point where the future is more exciting without him than with him (and by him I mean his active alcoholic self which is, of course, attached to his regular self). No matter how sad you may be now, there is nothing worse than that depressed feeling in the pit of your stomach you get when you have to face an active alcoholic everyday.