The enemy never despairs of your destruction, but you are now despairing of your own salvation. That is the very snare he set when he first whispered those terrors into your soul. To hear warnings from God is a dreadful thing, but to let them drive you to letting go of Faith altogether is to hand the victory to the seducing spirits Saint Paul spoke of, those that cause men to depart from the faith in latter times.
Consider Abraham. When the command came to offer Isaac, it seemed that God’s promise and God’s command stood at war with each other. Human reasoning would have cast him into confusion blacker than yours. Yet he did not measure the power of God by human reckonings. He accounted that God was able to raise him up even from the dead. Your own warning, as terrible as it sounds, is not a decree of final despair unless you make it one. God’s power is not bounded by what your eyes now see coming to pass.
Saint Paul, when he spoke hard truths to Israel and piled up accusations from the prophets, was careful not to wall them off from the faith by driving them into despair. He showed that the fall was not incurable, that a greater purpose was unfolding. So too must you see your state. The very fact that you are crying out, that your heart trembles, is not proof of your final ruin. The palsied man heard first, "Be of good cheer, thy sins be forgiven," before his body was healed. Hidden faith was proclaimed by the cure. Do not let the terror of the woe you foresee drown the faith by which you now call upon God. The time for despairing is not yet, so long as the contest still runs and the prize hangs in the balance. Draw near boldly, bringing only faith, and do not say in your heart, "Who shall descend into the deep to bring me up?" The Lord is able to raise even from the dead those things that seem utterly lost, and to quench the violence of any fire kindled against you.