In William Faulkner's "Barn Burning," Sarty's actions in the last portion of the story reflect a characteristic of human nature. All the while Sarty has lived with his family, miserably poor and constantly moving, the son to a selfish and vindictive man (Ab Snopes), he has tried to remain loyal to his father, even when asked to lie to the authorities. However, as time passes, Sarty starts to struggle between remaining loyal to his "blood relation" or doing the "right" thing.
We are aware of the struggle when the story begins and Sarty is saved from having to lie about his father's barn burning. His father accuses Sarty of almost telling the truth in the "court," and hits Sarty across the face. Sarty realizes that his father was right. This foreshadows Sarty's behavior at the end of the story.
Once again the family has moved, working now for the de Spain family, living on their property. But even from the beginning, Ab is antagonistic toward his employer, and when de Spain plans to make Ab pay for purposely ruining a rug in the main house, Ab decides to burn the de Spain barn. Sarty chooses to warn the de Spain family. To avoid being caught himself, Sarty begins to run as if he was running for his life. He stops when he hears three shots ring out, crying, "Pap! Pap!" and "Father! Father!" (We can infer that his father has been killed.)
In the excerpt at the end of the story, Sarty has finally stopped running. There are no signs of pursuit from behind; there is no glare from a burning barn. Sarty faces the dark woods, symbolic of the unknown—his future. His breathing is still a little shaky, but...
...the grief and despair [were] now no longer terror and fear but just grief and despair.
Sarty thinks about his father, and typical of human nature, Sarty tries to find something positive to believe about his father who is now dead. This is similar to the common characteristic of people—either to say nice things about someone when he (or she) is dead (even if he was the devil himself when alive), or to try to remember the person as better than he was, regardless of what he had done.
Sarty cannot shout his sentiments, but only says them aloud...
He was brave! [...] He was! He was in the war! He was in Colonel Sartoris' cav'ry!"
The truth, of which Sarty is unaware, is that Ab had no sense of loyalty and never supported one side over the other in the Civil War. He was loyal to no one but himself, simply taking plunder ("booty") from whichever side had lost it. In light of this lack of knowledge, Sarty typically tries to remember the best of a man who showed little regard for his son, or the welfare of his family. Sarty is still feeling the impact of choosing to do the moral thing as opposed to being loyal to family—even someone who may not have deserved it.
The dawn approaches and nature comes alive, and this is symbolic of the new life Sarty is about to begin. He can leave his painful memories behind. He has come out of his childhood a better person. He can leave the doubt, fear, abuse, and abject poverty in the past, and make his own way. He better knows himself now, and when he starts on his journey—away from the barn burning—he looks toward the sun, symbolic of hope, and...
He did not look back.