I don't have solutions, unfortunately, just chiming in to say that I have been experiencing the depression as well! (and I'm also not working right now, which is not helping at ALL). Out of curiosity, why would helping other people plan trips get you in trouble? Trying to help people solve their vacation problems with thoughtful planning is what has been keeping me sane and giving me a good outlet the past couple weeks. I figure I'll try and get good at doing it now, and maybe try to monetize it later. Or just do it for fun
My layman's theory on the cause of Post Disney Depression is this: while we are in the theme parks, we are overloaded with a TON of new stimuli - we're riding thrilling rides, eating in new and different restaurants, dealing with the pressure and stress of crowds, seeing new areas of the parks, wrangling our family members, navigating different modes of transportation, sleeping in a new room, etc. etc. etc. We're also probably getting way more exercise walking around than we do in our normal life. Add in all the nostalgia and emotion that Disney is able to trigger in us, whether through familiar childhood characters or triggering memories from prior trips. Perhaps all these new experiences spike levels of adrenaline, cortisol, oxytocin, dopamine, serotonin, and/or endorphins in the brain, and keep them at high levels throughout the trip. Once we get back on the plane to go home, those levels of "happy" hormones would settle back to the normal levels you get just from your everyday life. Post Disney Depression is an emotional response to the "withdrawal" of these hormones.
Not a scientist, or a medical professional of any kind. Just some of the thoughts I had as I sat sadly on our Southwest flight from MCO back to Texas in March, reflecting that I'd NEVER felt so sad to leave a vacation before.