Regarding the topic at hand, I did succeed on my hike but I had a couple serious health issues, and I struggled off and on with burnout when various factors combined all at once to make the experience miserable (bugs, mud, rain, chafing, knee pain, illness, boring rocky trail, etc). I could cheerfully deal with any three or four of these factors at any given time, but when they all combine, there was definitely a sense of "why am I doing this?"
Yet you pushed on. As a result you're here telling us of your success. And, telling us how that came about, not why you quit. Another thing I find admirable is that you credit your ultimate success in part to other's behavior, others caring enough about you, and you allowing them into your hike, your life. That demonstrates a leadership trait. What you and the others found is the trail is not just about you or any one person. That's what makes the AT possible, many things and people coming together.
The people around me, and one in particular, helped me continue to want it. I started the trail solo and determined to be sociable but ultimately independent. Instead, if anything, the lesson for me was how to lean on my friends. Humbling for sure. So beyond the undeniable reasons to get off like a serious injury, I think the stumbling block that might have caused me to fail would be refusing support when it was offered.
That can be difficult for one inclined to be independent. And, that lesson carries over for you in your off trail affairs? If so do you feel better for it? You also chose to allow yourself to be humbled, not everyone will.
Good stuff!