Chapter 10 states that a Guru can "strike a nail over the lines of destiny." What does this mean in the context of devotion to a Sadguru?

The phrase "strikes a nail over the lines of destiny," as mentioned in Chapter 10, signifies that a true Guru has the power to change a devotee's fate. The chapter explains that by placing complete faith in the Sadguru's feet, one's destiny can be altered for the better. This devotion is portrayed as a powerful force that can destroy the worldly existence (Samsara) and help a devotee overcome the three types of miseries. Just as one trusts a boatman to cross an ocean, Chapter 10 advises trusting the Guru to cross the ocean of existence (Bhavasagar), rendering other complex spiritual or intellectual practices unnecessary.