I hope you are using the book True Devotion to Mary in your preparation for consecration. In it, St. Louis de Montfort details his whole spirituality behind Marian consecration. It is so much more than the recitation of a few prayers; it should involve a complete change of heart, so that you are willing to give up anything of the world that is separating you from Christ.
"The first part of the preparation should be employed in casting off the spirit of the world, which is contrary to that of Jesus Christ.
"The spirit of the world consists essentially in the denial of the supreme dominion of God, a denial which is manifested in practice by sin and disobedience …
“It manifests itself by the concupiscence of the flesh, by the concupiscence of the eyes and by the pride of life; by disobedience to God’s laws and the abuse of created things. Its works are, first, sin in all its forms; and then all else by which the devil leads to sin; works which bring error and darkness to the mind, and seduction and corruption to the will. Its pomps are the splendor and the charms employed by the devil to render sin alluring in persons, places and things.”
Clearly, it will take much more than the recitation of a few prayers to accomplish this monumental task (which is a lifelong process)!
The spiritual exercises recommended by St. Louis de Montfort for the twelve preliminary days include:
“Examine your conscience, pray, practice renouncement, mortification, purity of heart; this purity is the indispensable condition for contemplating God in Heaven, to see Him on earth and to know Him by the light of faith.”
So, as you suggested, fasting and depriving oneself of worldly things can certainly be part of the process. Only you can decide for yourself what those things should be. One thing I found helpful was to meditate on the story of the rich young man who asked Jesus what he must do to gain eternal life (Matthew 19:16-24). As you recall, Jesus asked him to give up all he had to the poor and follow Him; the man went away sad, because he had many possessions. Take your Bible, find this passage, and take it to prayer. Ask God to reveal to you what it is that He wants you to give up. It may be something material, or it may be an attitude, a sin we cling to, a bad habit, pride, etc. “Lord, what am I clinging to that is separating me from You in any way? How do You want me to cast it off?”
