His sleep patterns! In the beginning, sleep is erratic, plagued by memories. His hyperthymesia means his dreams are just replays. As he finds purpose and a routine, his sleep, while never perfect, becomes more regulated. It's a small detail, but a powerful indicator of an internal state settling. The relentless replay of trauma in his dreams might never stop, but having a daytime purpose seems to give his mind other material to process. Sleep is a foundational human need, and his slow improvement there signifies a baseline level of safety returning to his psyche.