It is not so much the length of a prayer as the fervour with which it is said which pleases God and touches his heart. A single Hail Mary said properly is worth more than a hundred and fifty said badly. Most Catholics say the Rosary, either the whole fifteen mysteries or five of them, or at least a few decades. Why is it then that so few of them give up their sins and make progress in virtue, if not because they are not saying them as they should.
It is a good thing to think over how we should pray if we want to please God and become more holy.
1) Firstly, to say the holy Rosary with advantage one must be in a state of grace or at least be fully determined to give up sin, for all our theology teaches us that good works and prayers are dead works if they are done in a state of mortal sin. Therefore, they can neither be pleasing to God nor help us to gain eternal life. As Scripture says, "Praise is not seemly in the mouth of a sinner" (Ecclus. 15).
The praise and greeting of the angel and the very prayer of Jesus Christ are not pleasing to God when they are said by unrepentant sinners.
"These people honour me with their lips, but their heart is far from me" (Mark 7:6).
Those who join my confraternities (says Jesus Christ), who say the Rosary every day, without any contrition for their sins, offer me lip service only and their hearts are far from me.
2) I have just said that a person must "at least be fully determined to give up sin," 1) because if it were true that God only heard the prayers of those in a state of grace, it would follow that those who are in a state of serious sin should not pray at all. This is an erroneous teaching which has been condemned by the Church, because sinners, of course, need to pray far more than good people. Were this horrible doctrine true, it would be useless and futile to tell a sinner to say the Rosary, because it would never help him; 2) because they join one of our Lady's confraternities, or say the Rosary or some other prayer, without having the slightest intention of giving up sin, they join the ranks of her false devotees. These presumptuous and impenitent devotees, hiding under her mantle, with the scapular round their necks and the rosary in their hands, cry out, "Blessed Virgin, good Mother, Hail Mary," and yet at the same time they are crucifying Jesus Christ and tearing his flesh anew by their sins. It is a great tragedy, but from the ranks of our Lady's most holy confraternities souls are falling into the fires of hell.
We earnestly advise everyone to say the Rosary: the virtuous, that they may persevere and grow in the grace of God; sinners, that they may rise from their sins. But God forbid we should ever encourage a sinner to think that our Lady will protect him with her mantle if he continues to love sin, for it will turn into a mantle of damnation which will hide his sins from the public eye. The Rosary, which is a remedy for all ills, would then be turned into a deadly poison. Corruptio optimi pessima.
The learned Cardinal Hugues tells us that one should be as pure as an angel to approach the Blessed Virgin and say the Angelic Salutation. One day, our Lady showed herself to an immoral man who used to say the Rosary regularly every day. She showed him a bowl of beautiful fruit, but the bowl itself was covered with filth. The man was horrified to see this, and our Lady said to him, "This is the way you are honouring me. You are giving me beautiful roses in a dirty bowl. Do you think I can find them pleasing to me?"
- from The Secret of the Rosary, bySaint Louis-Marie Grignion de Montfort