Based on Chapter 10, what is the significance of a Sadguru in a devotee's life, and how can they alter one's destiny?

Chapter 10 powerfully illustrates the role of the Sadguru. It states that by placing faith in the Guru's feet, he can change one's fate, an act described as "striking a nail over the lines of destiny." The chapter explains that the Sadguru is the one eternal God, while all other gods are illusory. By seeing a devotee's faith, the Guru can grant liberation (Moksha) effortlessly, destroy accumulated and current karmas, and help the devoted cross the ocean of existence, just as a boatman helps one cross a worldly ocean. Pure service to the Sadguru can completely destroy the worldly existence (Samsara).