In Chapter 21, The Catcher in the Rye, what motivates Holden to finally go home, and why does his condition improve once he’s there?

Holden is desperately looking for some kind of stability and his little sister can provide that for him. In Chapter 21, Holden views his sister with a sense of wonder: he recounts with a sentimental appreciation each aspect of Phoebe's life, viewing her as a complete innocent. Of all the characters in The Catcher in the Rye, Phoebe is the only one that Holden treats with any degree of tenderness or respect. He listens intently to everything she says and does not react with the cynical observations that mark the rest of Holden's commentary. This is the most obvious manifestation of Holden's idealization of childhood.