When I was in high school and college, I used to work out all the time. I went to the gym four times a week and I would work out for a couple of hours each time I went. To help with my workouts, I read books and magazines. I took supplements. I charted my workouts writing down how much weight I was lifting and how many reps I was able to do.
While all those things helped, I don't think I would have seen any of the gains I saw had it not been for my workout partners encouraging me to show up to the gym and pushing me while I was there.
Just like we need workout partners to help us grow physically, we need workout partners in the church to help us grow spiritually.
If we want to grow as disciples and become mature believers, we have to have a community of believers around us challenging, encouraging, teaching, and building us up. We can't just get alone with Jesus somewhere; we have to have others in our lives because discipleship is relational.
Paul makes this clear in Ephesians 4:11-13 when he tells us that Jesus “gave the apostles, the prophets, the evangelists, the shepherds and teachers, to equip the saints for the work of ministry.” The saints were then to work to build each other up in the faith, helping one another become mature in Christ.
So as Christians we need Christian community. We can't do it on our own. For that reason we should invest in a local church. As well as we should strive to develop Christian friendships at school and in the community.