The authors discovered a recurrent theme, regardless of who gave the prophecies: God demands sacrifice. Whether it was His saints, or His mother, and often times Christ, Himself, speaking, God wanted sacrifices from us in order to give graces that would help in carrying our Crosses.
But just how does one make a sacrifice? A sacrifice, since Christ came, now took on different character and meaning than it did in Old Testament times.
A sacrifice is something that means something to you. It does not have to cause you pain, severe suffering, or great mental or spiritual problems. In fact, Saint Theresa of The Child Jesus, often known as "The Little Flower" (Theresa Martin of Liseaux) in the 1800s could not make heroic sacrifices. She simply did her "daily duty" to the best of her ability, honestly, and made small sacrifices.
For instance, if you feel that you must have coffee in the morning or have a great disposition for it, give it up certain days of the week. It can be on just Fridays, in honor of Christ's suffering in the garden and the first day of His Passion, if you like. But you make the sacrifice with a purpose.
The same could be said of cigarettes, a certain food, etc... something that means something to you. It can be small, but it must carry great significance to the one doing the sacrifice.
Many married couples practice sexual continence on a regular basis for Christ's honor. Others, still give sex up periodically to make repair to the great offended God, who is much too offended already, for those who practice sexual incontinence, especially for unmarrieds.
Your purpose should be stated and can go something like this. God's Mother gave us a pattern to follow. She said, "Make sacrifices for sinners and say often, especially while making a sacrifice:
Oh my Jesus, this is for the love of thee, for the conversion of sinners and in reparation for offenses committed against the Immaculate Heart of Mary."