Christians acknowledge that the trinitarian nature of God is a mystery that no amount of illustrating and explaining will ever be able to unravel. Rather than apologize for this, we view it as further evidence that God is indeed the kind of God we need: a God who is greater than we can comprehend.
The Holy Spirit is probably the most misunderstood person of the Godhead yet He is an important part of our salvation. It is a serious thing to offend Him. It robs us of peace and of usefulness. And if one continues to grieve and insult and quench Him, it may rob that person of his eternal reward.
Who is the Holy Spirit? Many regard Him as merely an impersonal force—a sort of divine influence emanating from God. In truth He is a distinct person in the God-head, with a special work and personality.