What is the most important lesson Ponyboy learns throughout The Outsiders and how does it change him?

One could argue that the most important lesson Ponyboy learns throughout the novel is to not judge others strictly on their appearances. Pony learns to exercise perspective, which allows him to sympathize with others, particularly people from different backgrounds. Toward the beginning of the novel, Ponyboy is quick to judge members of the Soc gang, his oldest brother, and Dally. Pony initially believes that the Socs live perfect lives and do not struggle, feels that Darry doesn't care about him, and thinks that Dally has no redeeming qualities.
As the novel progresses, Ponyboy has enlightening conversations with Cherry and Randy Adderson, which alter his perception of the Socs and allow him to understand their different struggles. Ponyboy also discovers that Darry truly cares about him following the church fire and sympathizes with his difficult life. After spending time with Johnny, Ponyboy begins to view Dally in a positive light and agrees that he is a gallant individual. Overall, Ponyboy learns not to judge others strictly on appearances and to exercise perspective. Ponyboy's increased perspective and sympathy for struggling adolescents motivates him to write the story The Outsiders.