Zac Poonen emphasizes the transformative power of the New Covenant compared to the Old Covenant, highlighting that the Old Covenant was limited in leading people to true inward righteousness, peace, and joy. He illustrates this by comparing the transition from British rule in India to the freedom of a republic, stressing that believers often fail to grasp the significance of living under the New Covenant. Poonen urges Christians to embrace honesty about their inner lives and to love the truth, as this is essential for spiritual growth and overcoming sin. He warns against the dangers of self-deception and emphasizes the importance of inward righteousness and a consistent Christian life, which is marked by joy and peace through the Holy Spirit.