Here’s from The Secret of the Rosary, by St. Louis Marie de Montfort on How to pray the Rosary Well:
With purity of intention:
It is not so much the length of a prayer, but the fervor with which it is said which pleases Almighty God and touches His Heart. One single Hail Mary that is said properly is worth more than one hundred and fifty that are badly said. Most Catholics say the Rosary, the whole fifteen mysteries or five of them anyway or, at least a few decades. So why is it then that so few of them give up their sins and go forward in the spiritual life? Surely it must be because they are not saying them as they should. It is a good thing to think over how we should pray if we really want to please God and become more holy.
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 real concentration for God listens more to the voice of the heart than that of the mouth.
When the Rosary is well said it gives Jesus and Mary more glory and it is more meritorious for the soul than any other prayer. But it is also the hardest prayer to say well and to persevere in, owing especially to the distractions which almost inevitably attend the constant repetition of the same words.
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