Extract from THE ASSUMPTION: MARY IS THE VIRGO POTENS
(John Henry Newman, Meditations and Devotions, Part 1 [IV])
This is why the Blessed Virgin is called Powerful-nay, sometimes, All-powerful, because she has, more than anyone else, more than all Angels and Saints, this great, prevailing gift of prayer.
No one has access to the Almighty as His Mother has; none has merit such as hers. Her Son will deny her nothing that she asks; and herein lies her power. While she defends the Church, neither height nor depth, neither men nor evil spirits, neither great monarchs, nor craft of man, nor popular violence, can avail to harm us; for human life is short, but Mary reigns above, a Queen for ever.