What does my faith have to do with the Church?
No one can believe alone and by himself, just as no one can live alone and by himself. We receive the faith from the Church and live it out in fellowship with the people with whom we share our faith.
Faith is the most personal thing a person has, yet it is not a private matter. Anyone who wants to believe must be able to say both "I" and "we", because a faith you cannot share and communicate would be irrational. The individual believer gives his free assent to the "we believe" of the Church. From her he received the faith. She was the one who handed it down through the centuries and then to him, preserved it from falsifications, and caused it to shine forth again and again. Believing is therefore participation in a common conviction. The faith of others supports me, just as the fervor of my faith enkindles and strengthens others. The Church emphasizes the "I" and the "we" of faith by using two professions of faith in her liturgies: the Apostles' Creed, the creed that begins with "I believe" (Credo), and the Great Creed of Nicaea- Constantinople, which in its original form starts with the words "We believe" (Credimus).
(From the Catholic Youth Catechism question 24)