Jesus tells His followers in John 15:1-11 to Abide (or remain) in Him, for apart from Him, we can do nothing. Jesus gives us 3 main connections to Himself: 1. Prayer, 2. His Word (the Bible), and 3. His body of believers on earth (Christian Community, AKA the church). If we neglect any one of these connections, we are tearing ourselves away from the vine of Jesus, we become fruitless, and our spiritual lives start to wither and die.
This is why Christian Community is so important. We must unite around the core gospel message, the shared faith which makes us Christians and followers of Jesus, while leaving room for others' convictions. We must encourage one another, while we also hold one another accountable in love. We pray together and build one another up. This is Christian Community.