Based on the provided text, what is the significance of the 'divine plan' in the context of human happiness and hardship?

The source material from Chapter 14 introduces the concept of a "divine plan" to explain the universal nature of hardship. It states that even Ratanji, a man who seemed to be "swimming in an ocean of joy," was tormented by an inner worry. The text explicitly says, "See, this is the divine plan; no one has unmixed happiness. Everyone has some nagging worry or the other behind them." This suggests that hardship is an integral part of the human experience, designed to prevent arrogance and foster humility. It implies that challenges are not random but are woven into life's fabric to ensure that no one becomes complacent or believes they are above suffering, thus keeping them grounded.