Lots of things can go wrong on an extended hike, and you need to be careful of the whims, wishes, and demands of fellow hikers. Thru-hikers try to maintain HYOH, which means: Hike Your Own Hike.
Here's an example. I'd been hiking for several weeks with a fellow Appalachian Trail thru-hiker whom I'd met in Maryland. The hiker was from New Zealand and all he talked about was seeing New York City. He asked me to take him there and show him the sights. The last thing I wanted was to go anywhere near NYC. He got someone else to take him, and later I heard that they both left the trail for good right there. They never finished their planned thru-hike. Lesson learned: Hike Your Own Hike, not someone else's.
Another time, I was with several younger hikers in Hanover, NH, home of Dartmouth College. One of them knew someone in a fraternity on campus, and I was invited to join them for an evening when we went into Hanover to resupply. I thought about it, but knew it would be an unwanted distraction. The hikers and the fraternity made the news next day--arrests--alcohol related. I learned again, Hike Your Own Hike.
In my thriller, The Trail, the fugitive starts his extended hike with a bold escape plan. If he'd stuck to his plan, he might have gotten away with murder on the trail. He became distracted; he weakened. He forgot to hike his own hike!