YOU MAY ASK OUR LADY TO OFFER THE PRECIOUS BLOOD THAT SERIOUS SIN BE PREVENTED

O Holy and Immaculate Virgin Mary, offer to the Eternal Father the Precious Blood of thy Divine Son for the intention that one mortal sin may be prevented this day (or this night). 

On a personal level, I have need to pray this prayer where I ask Our Lady to offer to the Eternal Father the Precious Blood so that I may not sin mortally. 

But this prayer also educated me as to how we pray for sin to be prevented. All of us may ask of the Virgin Mary to offer her Son's Blood to God the Father that mortal sin may not be committed. When you or I offer the prayer, we may leave it open, and ask that the grace may be given to whomsoever the Eternal Father chooses, but we may also ask that the grace be given to a specific soul, perhaps a loved one or someone one is called to pray for.