The state of mind was a concept that often appeared in novels. It could refer to a person's emotional state, inner feelings, and way of thinking. When writing, one could describe the protagonist's state of mind to show the development of a story and the shaping of the character's personality. Here are a few possible ideas: 1. Description of the protagonist's mood changes: Through the description of the protagonist's mood changes, the development of the story and the shaping of the character's personality are shown. For example, when the protagonist felt sad or angry, he could describe how his mood changed, how his emotions fluctuated, how his way of thinking changed, and so on. 2. Demonstrate the protagonist's inner feelings: By describing the protagonist's inner feelings, show his emotional state and inner feelings. For example, when the protagonist felt lonely or helpless, he could describe how his mood changed, how low his mood was, how sensitive his inner feelings were, and so on. 3. Use metaphor and symbolism to express the protagonist's state of mind. For example, the protagonist's mood was likened to the tip of the iceberg, his psychological state was likened to a black hole, and his loneliness was likened to the loneliness of the deep sea. This technique allowed the reader to better understand and feel the protagonist's state of mind. When writing, there are many ways to express the protagonist's state of mind so that readers can better understand the story and character. At the same time, he should pay attention to not over-emphasizing or exaggerating the protagonist's emotions while expressing his state of mind to maintain the narrative style and plot tension of the novel.