What it was which led to the termination of religious prospects so flattering, it is difficult to state with entire confidence. There is some reason for thinking, however, that the love of God, not far from this time, began to be disturbed by the accession and influence of a love, which was more mixed and earthly in its origin. She relates that her father with his family left the city of Montargis, in order to spend some days in the country; and that he took with him a very accomplished young gentleman, one of his near relations. This young man, of whom she speaks in high terms for his religious sentiments, as well as his intellectual and other accomplishments, became much attached to her. She was still young, being only in her fourteenth year. She gives us to understand, that this individual, notwithstanding the circumstance of her immature age, made propositions of marriage. And this, after a suitable time, would probably have been the result, with the cordial consent of all the parties concerned, if it had not been met by the obstacle, that their relationship was so near as to bring them within the degrees of consanguinity, in which marriage is prohibited in the Catholic Church. This obstacle, it is true, could have been removed by a dispensation from the Papal See; but, still it was one of so serious a nature, that her father did not think it proper to give his consent. Still they were mutually pleased, and spent much time in each other's company. It was at the time of this attachment, that she says significantly and penitently, that she "began to seek in the creature what she had previously found in God." But we will let her describe her spiritual declension in her own language.
In connection with a reference to her daily interviews with this young relative, she says:
I left off prayer. I became as a vineyard exposed to pillage, whose hedges, torn down, give liberty to all the creatures to ravage it. I began to seek in the creature what I had found in God. And thou, oh my God! didst leave me to myself, because I left the first and wast pleased, in permitting me to sink into the horrible pit, to make me see and feel the necessity of maintaining a state of continual watchfulness and communion with thyself. Thou hast taught thy people, that thou wilt destroy those who, by indulging wrongly-placed affections, depart from thee. Alas! their departure alone causes their destruction; since in departing from Thee, the Sun of Righteousness, they enter into the region of darkness and the shadow of death. And there, bereft of all true strength, they will remain. It is not possible that they should ever arise again, unless Thou shalt revisit them; unless Thou shalt restore them to light and life, by illuminating their darkness, and by melting their icy hearts. Thou didst leave me to myself, because I left Thee first. But such was Thy goodness, that it seemed to me, that Thou didst leave me with regret.
— edited from The Life of Madam Guyon (1847) Volume 1, Chapter 3.