Understanding Nostalgia in Childhood Memories

In the excerpt from a fictional novel, the protagonist reflects on her childhood memories as she returns to her hometown after years away. She describes the vibrant colors of her grandmother's garden, the joyful sounds of children playing during summer afternoons, and the bittersweet scent of roses that reminds her of both happiness and longing. This recollection serves as a catalyst for her to confront her past and consider how those experiences have shaped her identity. What is the central idea of this passage?