In 2022 the world population was estimated to be 8 billion people. As a writer you should consider each person in the world to be your teacher. If you observe their actions and behaviors, you will learn human nature. It’s a great study in human character, and the character of humans.
If you are writing fiction, know your characters intimately. What is their human nature? How will they respond to the different situations that you place them in?
Know too, that you are a teacher in this world. A member of the faculty of 8 billion. Tell your story. Write your story.