There are a number of ways to look at this questions. First, Antonia has a very happy, go lucky spirit, even when she has to accept work as a domestic. For instance, Mrs. Harling finds that her greatest fault "was that she so often stopped her work and fell to playing with the children". She races through the orchard and has hay-fights in the barn with Jim and the other children. She is thus able to overcome the meager circumstances that killed her father and made her mother bitter. Her existence on the prairie is one of world left behind and the journey toward cultural reorientation and adaptation.
Further, she is also able to overcome her status as a woman wronged by Larry Donovanwhodeserts herandhischild. Thenarrative is quite clever in this regard, because on a textual level, of course, she finds happiness through her marriage to Cuzak with whom she has more children. On a symbolic level she is thus elevated to the status of a fertility goddess who has the power to bring forth life and turn her circumstances around again.
Antonia has a passionate internal nature that allows her to thrive under any circumstances. Raised in poverty by weak parents, she nevertheless manages to make a way for herself throughout the course of the novel. Although Antonia is forced to work as a servant, left pregnant at the altar by Larry Donovan, and works herself to exhaustion as a wife and mother, her optimism never wanes. This attitude puzzles the novel's narrator, but Jim ultimately determines that Antonia's physical strength comes from her emotional strength. He explains that "all the good things of her heart came out in her body, that had been so tireless in serving generous emotions."