The body of Christ was instituted by our Lord and saviour. It is vitally important that we are attached to the body of Christ in order to function as a body of believers as God ordained.
Just like a human body has individual parts that work together, the church is comprised of individuals that should be functioning together as a whole body, not as separate limbs so to speak.
The enemy will do all that he can to cause hurt and offence, thereby erroneously convincing individuals that they are better off going it alone and separate from the body. However, once we understand God’s perspective on being part of His body, we have a better understanding of the great importance of being securely attached to the body.