God will crown and bless your efforts because of your sincere and heartfelt intention to cease offending God by this particular sin, even if you may fall into this sin again, it is your desire and intention to love and please God done in love that will bless you greatly.
I am presupposing that you confess this particular sin in the Sacrament of Reconciliation, each time you confess it with a clear intention to try not to repeat it, you receive graces in the confessional to resist the temptation not to sin this particular sin again…‘and with the help of Thy GRACE, I will try not to sin again’ (Act of Contrition). I am also presupposing that you are creating an environment for yourself where you can avoid the near occassion of this sin, that is removal of all obstacles that may lead you to commit this sin.
I am also presupposing that you are praying for graces to resist this sin from Jesus, The Holy Spirit and God the Father and that you are also seeking the intercession of all the angels and saints that you feel an affinity to and also your Blessed Mother Mary…you have alot of help there to rid yourself of this sin!!
So if you are doing all of this, then why fasting? Are you in good health enough to miss a meal everyday for 40 days? If you are a parent who has young children, extended fasting of this fashion is not recommended, because you have to be in good health, mind and body to fulfill your duty to God, to care for them.
It is true great graces are bestowed upon a soul that fasts. Though dear friend a fast of 40 days is extreme and difficult (it takes great graces to fast, especially for something this long, Jesus Himself fasted for 40 days and 40 nights) and if you are unable to achieve it, you may then feel a sense of never being able to conquer this sin, which is not true, as all things are possible in the Lord. If I was you, I would go before the Blessed Sacrament and keep an Holy Hour when work permits, and ask the Lord Jesus for all the graces possible to resist this sin and rid your life of it. I would then promise Jesus to fast every Friday for nine months for the grace to resist this sin and rid your life of it and for love of Jesus who suffered on Good Friday. This would be more realistic, achieveable and demonstrate clearly to our Lord that you are sincere of heart and that you are willing to sacrifice in order to be blessed with graces to conquer this sin.
Dear friend, my heart melted when I read your post, your heart is known to Jesus, He knows how serious you are in ridding yourself of this sin and God loves you always the same whether you sin or not, He will bless and crown your intentions, trust Him that He will. Your desire is so bold and sincere within you that you would desire such a sacrifice of yourself to please your Jesus, He will love your heart for this.
Pray, hope in Him and don’t worry, the Lord knows your heart and loves you, He desires your happiness and if it is to be free of this sin that will bring you happiness and God deems it essential for your salvation, then by much prayer and love your sin will be taken from you.
I will pray for you. At the end of the day it is up to you what you decide to do, but before you embark on this fast if you still deem it necessary, speak with your Priest when you go to confession and ask Him about it. I am sure He will deter you from such an extreme fast, purely because you are so contrite and sincere in your heart, this alone is enough to warrant blessings and graces from the Lord. You feel this sin requires such a fast because it weighs heavily upon you, before you carried this sin, our Lord did on the Cross. Believe in the Sacrament of Reconciliation and it’s power of absolution and the graces bestowed upon you each time you confess a sin.
My heart, prayers and love is with you
God Bless you and much love and peace to you