Go backpacking. I go crazy without it too. It slowly creeps up on me over months. If you haven't done it before, I wrote this to help: http://knol.google.com/k/how-to-backpack
I do that quite often, but never alone (I'd creep out while while staying in a tent at night alone with idea, that there might be bears nearby, even if it sounds funny). And it cannot be done frequently enough, over months... four or five days are already enough.