Prayer well made gives much pleasure to the angels, and therefore it is much assisted by them; it gives great displeasure to the devils, and therefore is much persecuted and disturbed by them. -St. John Chrysostom
The same Saint says that the angels have a high esteem for him who renders himself intimate with God by prayer; that while he is making it, they stand beside him in perfect silence; and when he has finished, they praise and applaud him.
Souls that have no habit of prayer, are like a lame and paralytic body, which, though it has hands and feet, cannot use them. -St. Teresa
St. Teresa proved this by her own experience; for, having abandoned prayer for some time, she began to fall into certain faults and defects, from which, though they were slight, she could not free herself, — rather, she went daily from bad to worse. She was herself obliged to say that she was on the road to perdition, to which the Lord told her she would have come, if she had not resumed prayer.
There is certainly nothing more useful than prayer. Therefore, we ought to entertain great esteem and love for it, and employ every effort to make it well. -St. Vincent de Paul
Text from A Year With the Saints (New York: P.J. Kenedy & Sons, 1891).