That familiar prayer of the Rosary, the Fatima prayer, reminds us of the fearful reality of Hell: "O my Jesus, forgive us our sins, save us from the fires of hell, lead all souls to heaven, especially those in most need of thy mercy". The Roman Canon, too, implores the Heavenly Father to "Grant us... peace in this life, save us from final damnation, and count us among those you have chosen." It may be an unpalatable dogma of the Church, but the reality of the existence of Hell is indisputable, in fact Our Blessed Lord, so full of mercy, so compassionate, so loving, makes it clear that Hell exists: "...if your foot causes you to sin, cut it off. It is better for you to enter into life crippled than with two feet to be thrown into Gehenna. And if your eye causes you to sin, pluck it out. Better for you to enter into the kingdom of God with one eye than with two eyes to be thrown into Gehenna, where 'their worm does not die, and the fire is not quenched.'" (Mark 9:45-47)
The line between life and death is finer even than a hair's breadth, and the reality of our eternal destiny no further away, how important then that we strive to live in God's grace and avoid the sin which can jeopardise our eternal salvation. As Jesus reminds us, once more: "For what shall it profit a man, if he gain the whole world, and suffer the loss of his soul?" (Mark 8:36) Nothing this world has to offer, no pleasure, no relationship, no self-indulgence, no desire of ours is worth losing our soul, is worth putting our salvation at risk.
Mortal sin is so serious that the Church teaches the following: "It results in the loss of charity and the privation of sanctifying grace, that is, of the state of grace. If it is not redeemed by repentance and God's forgiveness, it causes exclusion from Christ's kingdom and the eternal death of hell, for our freedom has the power to make choices for ever, with no turning back."(CCC para. 1861)
I think it was Archbishop Fulton Sheen (I may be wrong) who told the story of the nun showing the non-Catholic around the Church, and when the non-Catholic came to the Confessional box he asked: "Sister, what is this?" to which she replied, humorously: "The fire escape!" The story, true or not, makes a valuable point - no soul need ever go to Hell, no matter how grave its sins, God has provided the Fire Escape in the form of the Sacrament of Confession, He offers us the means to remain in His grace, indeed to grow in grace, to be reconciled to Him if we fall, and to avoid the greatest human tragedy of all: eternal damnation.