About two weeks into a long tour, you've gotten a system down, intentionally or not. A morning routine of what to do and in what order, an evening routine of pitching, eating, and whatever else you like to do (I like writing a journal). A routine on resupplying; how often, where, what to get. When to take a break during the day, for how long, for what purpose.
Once you've developed a system and settled into it, the ride gets a lot easier. Just so happens two weeks is about the same amount of time it takes to physically adjust to the rigor of a long tour.
It's the second week of a long tour that's the hardest. You haven't gotten all the way in shape yet, nor developed your system, and the excitement you had during the first week has worn off.