Nope, you're not alone.
It's the one aspect of touring that there is very little information about (that I can find, anyways).
Everyone is different and what works for one, may not work for another.
Me? I'll force myself onto the bike and go for a ride - a lot of the time I won't want to, but once I'm out I'm glad I did. A few times out and it becomes self reinforcing.
(When I started commuting on the bike was best of all because I
had to ride!)
Give the write up a shot - even if only a pen and paper and look at photos. It's a bit like a hill, tough at the start, you survive then it's all downhill!
Other things I've done is to read other people's accounts of similar routes or use the distance covered as inspiration for the next adventure.
With absolutely no medical training behind me, I'm convinced that the exercise, the fresh air and the new landscapes energise the body and returning home causes the body to slump.
At home, we can still get fresh air and exercise, we just need a bit of imagination to look anew at familiar landscapes.
Of course, recreating the "touring experience" at home can help too - anyone for a Guinness out of a pot?
Now that I know you're going to do a write up.....
Pull your feckin' finger out!!!! I've been waiting ages for this one!
(Meant in the nicest possible way!)
The very best of luck to you