The sermon emphasizes the pursuit of joy as a central goal for believers, rooted in a direct experience of God's presence and manifested through fellowship with Him and with other Christians. Drawing from 1 John, it highlights the importance of recognizing God as light, confessing sin, and embracing the divine nature bestowed upon believers, ultimately leading to a life characterized by obedience to God's commandments and a desire to share His truth with others, thereby illuminating the world with His light and experiencing the fullness of joy.