Star Wars: The Last Jedi - 39 Things We Learned From The Director's Commentary
17. Mirror Cave
Johnson talks about having lunch with Larry Kasdan and meeting JJ Abrams Michael Arndt, but that most important was he spent time hanging out with Rick Carter, who he describes as the "unseen Yoda behind this sequel trilogy".
The pair spent a couple of weeks talking about the movie: “If you know Rick, you know that when you’re talking with him about story you aren’t talking about action scenes, set-pieces, toys… you’re talking about what matters to you in the story, you’re talking about the mythic stuff behind it all, images that matter to you, how it relates to your experience." It was very important that that was the first conversation Johnson had about his story.
The image in the cave with the endless line of Reys, is all about her finding herself, wondering 'Which one am I? Where's it going to end? Is it going to define me?' That is supposed to represent adolescence. The Hero's Journey, Johnson says, isn't about literally becoming a hero, it's really about the transition from childhood to adulthood, and finding your place in the world.