Answer:
Anne Frank is expressing her thoughts and feelings about the changes she is going through as she reaches puberty. She has learned about the physical changes that girls her age experience and is fascinated by the "miracles" taking place in her body. She describes these changes as a sweet secret that she treasures and longs for, despite any associated pain. This shows her appreciation and excitement for the natural progression of her body, as well as her developing sense of self and identity.