David Wilkerson emphasizes the challenge of self-forgiveness, illustrating this struggle through the life of King David, who, despite being forgiven by God, grappled with guilt and lost his joy. Wilkerson highlights that even when sins are forgiven, the burden of self-condemnation can persist, leading to a loss of joy in one's spiritual life. He also shares the transformative experience of Hudson Taylor, who learned that true faith and joy come from resting in God's promises rather than striving for them. Ultimately, the sermon encourages believers to accept God's forgiveness and extend that grace to themselves, allowing the joy of the Lord to flourish in their lives.