The play is full of passion, love, and tragedy. It is clear that Shakespeare was deeply invested in the story and the characters. He felt strongly about the themes of the play, such as the power of love and the destructiveness of hatred.
It is also possible that Shakespeare was influenced by his own personal life when writing Romeo and Juliet. He had recently lost his son, Hamnet, and may have been feeling grief and loss. This could have contributed to the play's tragic tone.
Ultimately, we cannot know for sure what Shakespeare was feeling when writing Romeo and Juliet. However, we can say that he was a deeply passionate and talented writer who was able to create a timeless masterpiece.