Answer: (Summary with text evidence) - Tris embarks on a solitary walk to Dauntless headquarters, a familiar journey she has taken before. She recalls her first trip there alone, on the verge of throwing herself off the roof, "the first time I went to Dauntless headquarters I was also alone, but in a crow, standing on the edge of the roof in just my Abnegation shirt, about to throw myself into a life I knew nothing about." As she makes her way, she takes in the sights of a worn and cracked city and finds comfort in the familiarity of her surroundings. She searches for the hole that led her to become a part of Dauntless and to save her family, "I am looking for the hole I jumped into, once to become Dauntless and once to save my family."
Following the train tracks, Tris comes across the familiar place where the tracks curve around a rooftop, and she spots the hole in the space between two brick-and-glass buildings. The hole seems smaller than it did before, but Tris realizes that it may be due to her personal growth and the challenges she has faced, "Maybe it's just that I feel larger now, because so much has happened since I last saw it, feel like more of a person, more of myself, now that I have made difficult decisions and lost people and then almost lost myself, but not quite."
Undeterred, Tris walks up to the edge of the hole to make sure there is a net at the bottom, then runs a few steps and launches herself into the emptiness. As she falls, she feels like the "Dauntless compound is a creature and this is its mouth." Fortunately, the net catches her, cradling her instead of stinging her like the last time she jumped, and she hooks her fingers in the spaces to pull herself to the edge.
Explanation: (Shorter summary without text evidence) - Tris walks alone to the Dauntless headquarters, remembering the time she went there alone for the first time and was about to throw herself off the roof. She follows the train tracks and finds the hole she jumped into to become Dauntless and to save her family. The hole seems smaller now that she is bigger and more herself after making difficult decisions and losing people. She jumps into the hole, lands in a net that cradles her, and pulls herself to the edge.