Agnes speaks: "Daughter, stand firm and do not relapse, for a serpent lies at your heels ready to bite. Yet, do not rush unduly ahead either, for the tip of a sharp lance is in front of you, and if you advance at the wrong speed, you will be wounded.
What does a relapse mean if not letting trials lead to regrets about having taken on a more austere and wholesome way of life and to a desire of returning to old habits and delighting the mind with dirty thoughts? Such thoughts, even if they give some pleasure to the mind, only obscure every good thing and by degrees lead away from all goodness. Nor should you rush unduly ahead, that is, punish yourself beyond your strength or imitate the good works of others beyond your capacity.
God has ordained from eternity that Heaven should be opened to sinners through works of love and humility, yet by preserving moderation and discretion in every way.
Now, then, the envious devil persuades the imperfect man to fast beyond his strength, to promise to do unaccustomed things that he cannot manage, to desire to imitate more perfect models without considering his own strengths and weaknesses. The devil does this either in order that, when the man's strength fails him, he should continue with his badly begun vows out of human embarrassment rather than for the sake of God, or in order that he should quickly give up the struggle because of his indiscretion and weakness.
For this reason, use as your measure your own self, that is, your strengths and weaknesses, since some people are stronger by nature, others weaker, some more fervent by the grace of God, others keener due to good habits. Hence, regulate your life in agreement with the advice of God-fearing men, so that the serpent does not sting you due to your thoughtlessness, and so that the poisonous tip of the sword, that is, the poisonous suggestion of the devil, does not delude your mind so as to make you want to seem more than you are or long to become something beyond your strength and powers.
There are, indeed, some people who believe they can reach Heaven by their own merits, and God spares them from the devil's temptations due to His hidden plan. There are others who think they can make reparation to God for their transgressions with their own works. The error of all of these is altogether damning, for even if a person were to kill his body a hundred times over, he could not make up a thousandth of the account he owes to God, because it is God Who gives us the ability and the will, seasons and health, Who fills us with a desire for the good, Who gives us riches and honor, Who kills and gives life, raises up and lays low. All things are in His hand. Hence to Him alone should all honor be given, and no one deserves to be counted for anything before God.
Since you are wondering about the lady who came for indulgences but was corrupted, I answer you: There are some women who have the virtue of continence but do not love it. They experience neither a great longing for pleasure nor violent temptation. If honorable proposals of marriage were made to them, they would accept. However, since no great offers are made to them, they look down on lesser offers. In this way, continence sometimes gives rise to pride and presumption, which, by divine permission, leads to a fall, such as you have now heard.
If a woman were so minded as not to want to be stained even once, not even if the whole world were offered her, it would be impossible for such a woman to be left to shame. If, however, in His secret justice, God permitted such a one to fall, it would rather lead to her reward than to sin, provided that she fell against her will.
Know, then, that God is like an eagle that from on high views everything down below. If an eagle should see anything rising up from the ground, it immediately swoops down and snatches it. If it catches sight of something poisonous coming against it, it would pierce it like an arrow. If something unclean is dropped on it from above, it gets rid of it with a great shake just like a goose does.
God acts like that as well. If He sees human hearts rising against Him due to the weakness of the flesh or the devil's temptations against the will of the spirit, He immediately swoops down through an inspiration of contrition and penance and brings it to naught, making the person return to God and come to Himself again. If the poison of carnal desire or greed enters the heart, God quickly pierces the mind with the arrow of His love, so that the person does not persevere in sin and get separated from God.
If some impurity of pride or the dirt of lust defiles the spirit, He shakes it quickly off, just like a goose, through constant faith and hope, so that the spirit does not become hardened in vice or the soul that is joined to God become stained unto damnation.
Therefore, my daughter, in all your feelings and actions, consider God's justice and mercy, and always keep the end in sight."