Costly spices give out their aroma most freely when they are bruised in a mortar; so the truths of religion have most influence upon the soul that ponders on them. One who meditates upon holy things is like a man striking fire with flint and steel; he strikes the stony heart with the keen edge of the understanding until sparks fly out, that is, good resolutions are elicited from the will. Meditation is only difficult until the Holy Spirit makes His gracious action felt. Like a vessel that must be propelled by toilsome rowing until a favorable wind springs up and inflates her sails, then the oar is no longer needed, for she runs swiftly before the breeze — so in meditation the powers of the mind must be exercised laboriously, until the Holy Spirit breathes upon the soul, guiding it and elevating it. If we strive to elicit a succession of beautiful thoughts and elaborate meanings, this is not prayer, but study. When once we have struck fire, let us toil no more, but forthwith kindle the torch.
By mental prayer we imitate on earth the occupation of the angels who constantly contemplate the face of God, and meditate on His perfections. The saints have bequeathed to us many books of meditations; if we read these attentively it is equivalent to prayer. Mental prayer must alternate with vocal prayer; these two methods of prayer are the two feet that carry us forward on the way to heaven. Meditation is a necessary preliminary to prayer; without it prayer will be imperfect, the needful devotion will be lacking
We obtain many actual graces in meditation; for as we receive light and warmth when we stand by a fire, so by meditation upon the truths of religion the mind is enlightened to see the worthlessness of earthly things, the end of man, the rigor of the divine judgments, and the heart is inflamed with the love of justice. It is a furnace wherein the fire of divine charity is kindled, a door whereby divine grace enters into the heart of man. A soul that practices meditation is like a cultivated field which produces abundant fruit, a well-watered garden in which flowers bloom luxuriantly. He who neglects to ponder upon the truths of religion knows nothing of their force; his spiritual sight is dimmed, he is engrossed with the things of earth. With desolation is all the land made desolate, because there is none that considereth in his heart (Jer. 12:11). The subjects chosen for meditation ought to be those which have most power to attract and influence us, and to these we should frequently recur. Thus bees alight upon the flowers which contain the sweet juice whence they make their honey. Meditation is a means of attaining perfection. St. Ambrose says daily meditation is the antidote for tepidity. It was the foundation of the conversion of St. Ignatius and other saints. St. Teresa declares that mental prayer and mortal sin are incompatible; they exclude one another; one or the other must of necessity be given up.