In order to pray well, it is not enough to give expression to our petitions by means of that most excellent of all prayers, the Rosary, but we must also pray with great attention, for God listens more to the voice of the heart than that of the mouth. To be guilty of willful distractions during prayer would show a great lack of respect and reverence; it would make our Rosaries unfruitful and make us guilty of sin.
How can we expect God to listen to us if we ourselves do not pay attention to what we are saying? How can we expect him to be pleased if, while in the presence of his tremendous majesty, we give in to distractions, like a child running after a butterfly? People who do that forfeit God's blessing, which is changed into a curse for having treated the things of God disrespectfully: "Cursed be the one who does God's work negligently." Jer. 48:10.
Of course, you cannot say your Rosary without having a few involuntary distractions; it is even difficult to say a Hail Mary without your imagination troubling you a little, for it is never still; but you can say it without voluntary distractions, and you must take all sorts of precautions to lessen involuntary distractions and to control your imagination.
To do this, put yourself in the presence of God and imagine that God and his Blessed Mother are watching you, and that your guardian angel is at your right hand, taking your Hail Marys, if they are well said, and using them like roses to make crowns for Jesus and Mary. But remember that at your left hand is the devil, ready to pounce on every Hail Mary that comes his way and to write it down in his book of death, if they are not said with attention, devotion, and reverence. Above all, do not fail to offer up each decade in honor of one of the mysteries, and try to form a picture in your mind of Jesus and Mary in connection with that mystery.
We read in the life of Blessed Hermann of the Order of the Premonstratensians, that at one time when he used to say the Rosary attentively and devoutly while meditating on the mysteries, our Lady used to appear to him resplendent in breathtaking majesty and beauty.
But, as time went on, his fervor cooled and he fell into the way of saying his Rosary hurriedly and without giving it his full attention.
Then one day our Lady appeared to him again, but this time she was far from beautiful, and her face was furrowed and drawn with sadness. Blessed Hermann was appalled at the change in her, and our Lady explained, "This is how I look to you, Hermann, because this is how you are treating me; as a woman to be despised and of no importance. Why do you no longer greet me with respect and attention while meditating on my mysteries and praising my privileges?"
Saint Louis de Montfort, Secret of the Rosary