Acharya Prashant addresses the root cause of nervousness in public speaking, explaining that the anxiety stems from the presence of an audience rather than the act of speaking itself. He demonstrates that while a person may feel comfortable speaking to a wall or a mirror, the presence of others introduces a fear of judgment. This fear arises because individuals often allow others to define their self-worth. He emphasizes that while people may be qualified to critique external things like speech quality, clothes, or academic marks, they have no authority to judge one's inner being or fundamental value.