So many people today deny sin, especially Original Sin, In addition, many sins are called "natural", such as sexual acts against nature. Cyril wrote on these problems and his words are as timely today as they were 1,800 years ago or so. Link is here.
The soul is immortal, and all souls are alike both of men and women; for only the members of the body are distinguished716. There is not a class of souls sinning by nature, and a class of souls practising righteousness by nature717: but both act from choice, the substance of their souls being of one kind only, and alike in all.
Sin is not inbred; sin is not a result of nature but free choice. We are not born doomed to die in sin. On the contrary, this entire Holy Week is about Christ's Salvific Action of saving us and allowing us to be restored as children of God and heirs of heaven.
But, this means that God's immutable laws are to be respected, not changed.
I know, however, that I am talking much, and that the time is already long: but what is more precious than salvation? Art thou not willing to take trouble in getting provisions for the way against the heretics? And wilt thou not learn the bye-paths of the road, lest from ignorance thou fall down a precipice? If thy teachers think it no small gain for thee to learn these things, shouldest not thou the learner gladly receive the multitude of things told thee?
Perfection demands a mental, intellectual involvement in one's faith life. Ignorance is not an excuse.
21. The soul is self-governed: and though the devil can suggest, he has not the power to compel against the will.
Satan cannot make you do anything against your will. This is key. However, you and I must strengthen our wills. Weakness of will is a result of original sin and it is part of our duty to learn how to resist evil and choose perfection, day after day. Hell is not a necessary choice. This is so important to understand.
One chooses heaven or hell; imperfection or perfection.
He pictures to thee the thought of fornication: if thou wilt, thou acceptest it; if thou wilt not, thou rejectest. For if thou wert a fornicator by necessity, then for what cause did God prepare hell? If thou were a doer of righteousness by nature and not by will, wherefore did God prepare crowns of ineffable glory? The sheep is gentle, but never was it crowned for its gentleness: since its gentle quality belongs to it not from choice but by nature.
One cannot excuse one's self concerning sin.
To be continued....