How does the story of Ratanji illustrate the book's philosophy that 'no one has unmixed happiness'?

The story of Ratanji in Chapter 14 serves as a powerful example of the philosophy that complete, unadulterated happiness is elusive for everyone. The text explicitly states this divine plan after introducing Ratanji as a Parsi merchant who was outwardly "swimming in an ocean of joy." Despite his vast wealth and charitable nature, he was tormented by the "crocodile of a difficult inner worry"—his lack of a son. This illustrates the theme that even those who seem to have everything can be plagued by a significant sorrow, preventing them from experiencing unmixed happiness and keeping them humble.