I saw this in a topic that was over a year old and typed a reply...then I realized it was over a year old XD...So how do you deal with that feeling of emptiness you have when you have to return to the real world after a convention? This is my suggestion:
I actually keep a scrapbook of every anime convention I have been to. It's fun picking out pictures of the convention to put in the book, and finding (ebay-ing) anime-themed stickers and decorations to put in there. Sometimes I even get the decorations for the new scrapbook pages at the conventions. It's a great way to remember all the weird or cool things you saw and did and immortalize them in a book you will probably keep forever. I had never done scrapbooking before when I started, but I started getting better at it and more creative over time. Among other things, I use pictures, con badges, stickers, ads, cutouts from convention books, and patches. You can also ask friends to write/type captions for you so that you have some of their memories in there, too. It always helps me with the post-con depression and I have something to look at whenever I want.
Here are some examples from my book. Apologies for being lazy and not editing my pajama pants out of some of them :)
You could also try looking up information on the next convention you will go to - I always go to at least two a year, so instead of being depressed over one, look forward to the next :) I always try to get together with my friends one last time (closer to home) post-con at the end of the weekend so we can talk about everything that happened there. After Otakon last year, some of us went to Dave and Buster's for some drinks and games. Just some thoughts.