What is Johnny's main message in his letter to Ponyboy in The Outsiders?

Towards the end of the story, Ponyboy opens the novel Gone With the Wind and a slip of paper falls out of the book. The slip of paper is actually a note that Johnny had written to Ponyboy while he was in the hospital. Throughout the letter, Johnny tells Ponyboy that he does not regret saving the children from the burning building. He then tells Ponyboy the meaning of the Robert Frost poem. Johnny explains the poem and compares it to Ponyboy and Dally's lives. Johnny says that staying gold essentially means remaining innocent. He encourages Ponyboy to stay innocent and to tell Dally that it is not too late to change his perspective on life. Johnny's main message throughout the letter is that Ponyboy should remain innocent and not grow up too quickly. He also wants Ponyboy to relay that message to Dally in order to give him hope.