Romans 12:5 so we, though many, are one body in Christ, and individually members one of another.
Why do many Christians fall away? Many do so from never developing their faith. This would include Bible study individually and with other Christians who are well grounded in the truth. Peter tells us to desire the word of God like a newborn baby desires milk (1 Peter 2:2) However, he instructs to grow more and more in grace and knowledge (2 Peter 3:18). Christians are to set the word of God deep in their hearts to defend against the wiles of the devil.
I think the devil works hard on believers to leave behind their love for the Bible and love for the brethren. He loves to isolate Christians from each other so they lose the strength that comes with fellowship and working together. Be very careful when you start losing the desire to be with the saints in worship and fellowship. Built into these things is the aspect of strength where people watch out for one another.
Don’t let the devil fool you into not spending time with faithful Christians. Look at these verses to see what the first Christians did: Ac 9:18-19; 10:48; 16:15; 16:33-34; 18:8, 11. We truly are part of one another for a God given reason.