How does the story of Ratanji illustrate the idea that no one has 'unmixed happiness'?

The story of Ratanji, a wealthy Parsi merchant, perfectly illustrates the principle that no one experiences unmixed happiness. As detailed in Chapter 14, Ratanji had vast wealth, property, and a generous spirit, making him appear to be "swimming in an ocean of joy." However, he was plagued by a "difficult inner worry" because he had no son, only twelve daughters. This narrative shows that even someone with immense material prosperity can have a nagging sorrow that prevents true peace of mind. The text explicitly states this is part of the "divine plan" and that everyone, no matter how fortunate they seem, has some worry following them.