Why do I ride so lousy after a tour? I'm a male, 44, "fast" (?) recreational cyclist, who has been doing week long -- mostly 50 to 80 miles/day -- tours for about 15 years.  While I love touring, I have come to dread the aftermath . . . namely, that for at least 6 weeks following the tour, I ride and feel like a, uh, piece of crap, for lack of a cleaner phrase.  Can't fully explain it.  Sort of like I'm running on fumes, or with one less cylinder.  Power output could be up to 15-20% less for a given hard effort, or so it seems.  I ride pretty well during the tour.  I take a week of recovery rides following it.  Seem to still feel OK then, its the second week that it really hits me.  I keep hearing how a tour -- or stage race -- will bring one's fitness "to a whole new level," etc.  All these years, and I have yet to experience anything close to that!  So, any ideas, suggestions, etc.?
Only things I can think of:  perhaps since I'm not doing hard intervals during the tour, I'm stating to lose fitness then? (My tours are usually in mountainous areas, so its not that I'm just riding easy, but I try to keep my pace on the climbs under control.) The recovery week following then exacerbates that loss?  Also, I'm a mailman who has to walk 7 - 8 miles/day up God-only knows how many hills and steps, which I guess makes getting a "full recovery" pretty much impossible.
My theory is endorphins. Our bodies generate them when we exercise. Or not, when we stop. All those days of steadily pumping out the good stuff makes the tour feel great but when I stop, ooops. I suggest you not try replacing them with synthetic endorphins as those are illegal and tend to be more addictive.

There's also a body habit transition, where a bunch of the cycles in my body are set up for big exercise every day and suddenly I'm back behind a desk 8 hours a day. Half an hour each way does not cut it, I'm barely warmed up by then. So I bloat (very thirsty in the morning but then water retention), feel stiff but twitchy, and after the first couple of days tend to lose interest in food. This is my body saying "hey, you used to exercise, what happened to that?" 

What works for me is: 


tapering the tour rather than spending the last couple of days riding really big distances to catch up after stopping to smell the roses earlier on
taking the long way home from work (ride an hour or more)
eat junk food when I get home (swap endorphins for sugar, fat and umami)
stretching (yoga, martial arts) 
taking one day mid-week to go for a long ride


For me this is pretty much automatic now, I get home and hit the supermarket for all the food I couldn't really get or prepare while touring and the long ride is often a freebie when I go to pick up all the extra cr... stuff I took but posted home mid-ride and is now sitting in a post office somewhere on the other side of the city. The twitchyness means I do tend to get out and do stuff, often after a tour I go into a burst of deferred maintenance around the house or just go for long bike rides.

One thing that I find helpful is to take a mid-week day off after I get back and do something energetic. That means I have two days behind a desk, a day running round, then another two days. It means I'm more able to actually sit behind the desk and focus.