Siddhartha undergoes subtle shifts in mood that mirror the titular character's turbulent feelings and reflects the challenges of achieving true knowledge. At first, the story presents an optimistic picture of the young Siddhartha, whose intelligence and attractiveness bode well for his future success. In the middle of the story, the mood shifts to one of turbulence and dissatisfaction (during both his ascetic and materialistic phases). The mood takes a further turn toward sadness when Siddhartha meets his son and discovers that he has been spoiled. This downward trend in emotion shows the depth of Siddhartha's struggle, but it also serves as a reminder of his resilience, because no matter how difficult his situation becomes he always continues to search for Nirvana.
Finally, when Siddhartha achieves enlightenment, the mood changes into one of fulfillment and joy. The final passages take on an exalted, quasi-religious quality. In Chapter 12, when Govinda learns of Siddhartha's enlightenment, he stares in awe at his long-lost friend:
No longer knowing whether time existed, whether this seeing had lasted a second or a century, no longer knowing whether a Siddhartha existed, or a Gautama, or I and Thou, wounded in his innermost as if by a godly arrow, whose wounding tasted sweet, enchanted and dissolved in his innermost, Govinda stood for a brief while, leaning over Siddhartha’s silent face, which he had just kissed, which had just been the setting of all formations, all Becoming, all Being.
This passage reveals Govinda's delight and wonder. As he connects with Siddhartha, he realizes the depth and power of enlightenment. He gets "wounded in his innermost" but the "wounding tasted sweet" and he recognizes it as necessary to his understanding of what has happened to Siddhartha. The mood here resolves into one of profound discovery—but rather than pure energetic excitement, there prevails a feeling of peace and contentedness. This moment completes the novel's arc from initial optimism, and then turbulence, all the way to peace and satisfaction. The changing moods throughout the novel reflect Siddhartha's level of happiness and make the story all the more moving.