Why do we need to go to Church to maintain a dynamic life of faith? The answer is a mystery, and there are probably a lot of reasons. But I found it interesting to see that even the early Church Fathers reflected on two elements of faith life - communal and private prayer. (The quote comes from The Path of Life and the reference is to Pentecost, as described in the book of Acts.)
"... the Holy Spirit is described as descending under the appearance of fire, individual tongues of flame resting on each of the apostles [and in my understanding, everyone in the room*]. Certain of the Church Fathers... have seen here a symbol of our daily relationship with God. On the one hand there is the single Spirit, binding us into one, so that we relate to God communally as members of a single Body. On the other hand the individual tongues of flame show that each of us has a private, personal and secret relationship to God which is unique and unknown to anyone else. It is important for us to realize that both elements, both communal and private, are needed in order to form a complete spiritual life." (p. 137)
*In my mind, there were 120 or so in the room on that day - based on the reference to 120 believers in Acts 1:15. But, in fact, the account in Acts 2 only says "they" - not indicating exactly who "they" were.