Here is an example to help you understand the efficacy of the Rosary. You remember the story of David who vanquished Goliath. What steps did the young Israelite take to overthrow the giant? He struck him in the middle of the forehead with a pebble from his sling. If we regard the Philistine as representing evil and all its powers: heresy, impurity, pride, we can consider the little stones from the sling capable of overthrowing the enemy as symbolizing the Aves of the Rosary.
The ways of God are entirely different from our ways. To us it seems necessary to employ powerful means in order to produce great effects. This is not God’s method; quite the contrary. He likes to choose the weakest instruments that He may confound the strong: “God chose what is weak in the world to shame the strong — Infirma mundi elegit ut confundat fortia” (1 Cor 1:27).
Have you not often met poor old women who are most faithful to the pious recitation of the Rosary? You also must do all that you can to recite it with fervour. Get right down, at the feet of Jesus: it is a good thing to make onself small in the presence of so great a God.
Dom Columba Marmion, Christ, the Ideal of the Priest