What role does joy play in the life of a believer?

Joy is a natural response of believers derived from understanding the grace and love of God through Jesus Christ. In John 15:11, Jesus speaks of His joy remaining in us, leading to fullness of joy. This joy arises from the knowledge of salvation and the intimate relationship we have with Him. It is not dependent on circumstances but is rooted in the assurance of our standing before God, which empowers us to express praise and worship, as depicted in Psalm 87:7 where every believer is viewed as a singer and player in gratitude for the springs of life found in Him.