From where does inner spiritual strength come?: from God or from a belief in God? The question doesn't bear thinking about; the God of Christianity is so obviously a creation of the imagination. To discover why we people feel the need to create such Gods, we must examine the operation of the ego.
Most of us regard egotism as consisting almost entirely of dominant behavior, as seen mainly in men. Yet submissiveness is equally egotistical, and is most common in women. Indeed, dominance and submission are the two primary means by which the ego finds security.
Submission is most satisfying when the object one submits to is super-dominant. Therefore, Christians have seen fit to create for themselves an all-powerful, all-knowing God - in their own image - to submit themselves to. Another cunning reason for the creation of such a God is so we might all be equal before him. This savage blow adequately disposes of the great individuals, and conveniently protects the Christian from standards. For now they can refuse to believe that truly wise men can and do exist, we being all equal before God.