I agree, plan your next trip...but I don't start thinking about it while I'm on my current trip-that would take away the current fun for me.
I also write a detailed trip report, it allows me to lose myself in how great our trip was, and also gives me something I can always poor back over and over to like a scrapbook when I get the Disney blues.
I also love listening to Disney theme park music, but I don't usually start doing that until a few weeks post-trip. Souveniers are great if you buy the right ones. I go to basin and buy a few special soaps that will last a few months, a new key chain that I'll have with me daily, car decals, and this time I got a WDW tote bag that I carry daily. So that way I get to take the World with me!