in ways you wouldn't believe.
Especially for any who feel that they have fallen away from the faith (though everyone is benefitted greatly). Just ask Mary to add you to her prayers of intercession. Jesus does listen to his mother's pleas. In fact, Christ's first miracle, the changing of the water to wine at the wedding feast at Cana, was done on the request of his mother even though He said that He was not yet planning to perform miracles. We should always offer prayers to The Holy Trinity, but our prayers are tainted by our earthly desires, and Mary offers to give her own intercession on our behalf even though she watched man torture and humiliate, and murder her son. God has honored her specially, and she is an incredible resource that is available simply if we just ask.
I heard it said by a wise person that when a sinner begins praying the rosary, one of two things happens fairly quickly. Either the person stops/decreases sinning or the person stops saying the rosary.