One of my favorite authors and speakers is Larry Crabb. I've heard him speak on several occasions, and his definition of spiritual community is one of the most powerful ideals he shares. He defines Christian community this way:
"Reaching with supernatural community power into the depths of another person's heart so that the evil in our hearts that rules so often unrecognized in how we relate is clearly identified and exposed as hateful and that the Holy Spirit is given full sway to release our appetite for the Father."
There's a lot in that statement. He expands on this statement further by saying the real battle to maintain community is helping one another overcome the suspicion that God is not good and that I need to take over. Sometimes we recognize that easily, other times we don't. One of the main purposes of Christian community in our small groups is to help encourage one another as we face skirmishes in that battle.
Part of helping one another is walking with one another through trials of all kinds. We need to help one another see that God often allows us to go through things that are very crushing and discouraging in order to get us to the point where we are hopeless and helpless before Him. At that point, we can know there is nowhere else we can turn but to the Lord. However, going through that process alone can be very discouraging and create bitterness rather than growth. That's why we absolutely need Christian community in order to truly grow. Where else can people really get into healthy growth processes other than in some type of intentional small group?