My advice to is this.
#1. Don't let the bottle be your best friend right now. Talk with your friends, go out, get out of town, go somewhere where no one knows your name for a couple of days. Kick back and forget about life for awhile.
#2. Go out, meet new people, and I know you can't forget her, trust me. I've never been engaged, but I have had one serious girl who took a big piece of me. What I did, I focused on me for a while. I did the things I couldn't do with her, I made myself happy. I went to sporting events with the boys, went out with my friends, took a trip here and there, but I did that to show her that I was okay, and that I had forgot about her. I still think about her every now then, but do I miss her? No. I enjoyed what we had, but I do not miss her, simply because someone out there will make 10x happier than she ever could.
#3. Refer back to #1. There are plenty of other things out there to do beside drink it away. Yes go out have fun with friends, but do not drink alone. Drinking alone and heavily will put in a very dark place you do not want to be. Trust me I did that. I found myself relying on the bottom of the bottle instead of the people around me who needed me and vice versa. Once I put down the bottle, then I started to return to my old self, and enjoy life.
Just my two cents,
If you need anything shoot me a pm here, I'll see what I can do.