1 John 1 : 4-5+7
4 And these things we write to you that your joy may be full.
5 This is the message which we have heard from Him and declare to you, that God is light and in Him is no darkness at all.
7 But if we walk in the light as He is in the light, we have fellowship with one another, and the blood of Jesus Christ His Son cleanses us from all sin.
True joy is found in the study of God's Word, the Bible. We thank God that the Gospel was written down and is accessible to us anytime, anywhere. Take for example, the truth of the Light.
Believers walk in the Light and thus, there is community that is brought about by God Himself. This allows for believers to have fellowship with one another, because there is nothing that separates them. (Romans 8 : 38-39) This is a community that is not brought about by the believers themselves. Therefore, they cannot undo that community. The Lord has asked His heavenly Father (not us!) for this community. (John 17 : 21) His prayer has clearly been answered and that should fill us with great joy.