Remember that Our Lord said:
"Fear not them that can kill the body; rather fear Him Who can both kill the body and destroy the soul in Hell."
Rehearse as often as you can the idea that you, a created being, would be so bold as to:
Sin willfully against the revealed will of God
Count as nothing all the graces you have received thus far
Have such disdain for Our Lord Jesus Christ and His Cross and Passion, Who suffered willingly so that sins might be forgiven and Heaven opened
Make such a poor example of yourself to others who might be scandalized by your offenses against Our Lord or who, God forbid, might be tempted to follow your lead.
Go find a Crucifix, preferably one that you have no ability or permission to remove. Kneel before it, stare at it, concentrate on every Wound and Stripe and droplet of Blood, and get it through your head that what you are seeing is NOTHING compared to the horrific, yet glorious Passion which Our Lord Jesus Christ undertook for an unworthy sinner like you.
Recognize that His love for you is such that His every pain and His burden of grief were offered to Almighty God for the redemption of your soul.
Then realize that the infinite worth of His Passion will guarantee your salvation if you cling obediently to Him and will likewise guarantee the terrors of Hell should you spurn Him.
Immaculate Heart of Mary, triumph soon!
Most Sacred Heart of Jesus, have mercy on us.