When one has received the Holy Ghost he has a companion who will constantly warn and teach and inspire him. (Moroni 10:5) If not driven away through uncleanness or other persistent wickedness the Holy Ghost will always bear increasing witness to gospel truth. The potency of his influence is emphasized in this explanation by President Joseph Fielding Smith:
The reason blasphemy against the Son of God may be forgiven, even if the Son be made manifest in a vision or a dream, is that such manifestation does not impress the soul as deeply as does the testimony of the Holy Ghost. The influence of the Holy Ghost is spirit speaking to spirit, and the indelible impression in one that brings conversion and conviction to the soul as no other influence can. The Holy Spirit reveals the truth with a positiveness wherein there is no doubt and therefore is far more impressive than a vision given to the eye.
Miracle of Forgiveness
Spencer W. Kimball
Elder Parley P. Pratt also described the effects of the Holy Ghost:“[His influence] quickens all the intellectual faculties, increases, enlarges, expands and purifies all the natural passions and affections; and adapts them, by the gift of wisdom, to their lawful use. It inspires, develops, cultivates and matures all the fine-toned sympathies, joys, tastes, kindred feelings and affections of our nature. It inspires virtue, kindness, goodness, tenderness, gentleness and charity. It develops beauty of person, form and features. It tends to health, vigor, animation and social feeling. It invigorates all the faculties of the physical and intellectual man. It strengthens, and gives tone to the nerves. In short, it is, as it were, marrow to the bone, joy to the heart, light to the eyes, music to the ears, and life to the whole being”