The whole reason sin is sin and condemned by the law of a loving God is that the consequences are deadly after being first hurtful.
Some sins are quiet and sneaky, easily hidden, easily rationalized into an old mental file cabinet. But these sins have consequences, shutting the sinner off from the blessings of humility, hearing God, understanding mysteries, communing with the Author and Lover of their soul.
They may have a bright smile, be able to quote scripture, pray in a public meeting... but have a dark secret vacuum inside. I have been one of those.
I have a good friend who is a devoted Christian with an effective ministry and a wide open love for God and His people. But in his younger years he was a horrible person with way too much experience in every type of open sin. The details are too awful to even mention here.
The result is that despite the wonderful forgiveness he enjoys, he bears the physical and mental scars of the things he did. They are permanent scars and he would be the first to tell any man or woman that sin is devastating, set against your life, your happiness, your peace, and your power. What you give to Satan is very difficult to reclaim. Many try and fail.
So how does this relate to the discussion? Very simple, the sins people commit will be extremely difficult to undo. Sometimes it is possible to contract an incurable disease, sometimes a man will shy away from preaching a hard line on fornication because his former conquests are close by and he fears the embarrassment. Sometimes a man has a child by a woman not his wife- "It was just once, we got carried away!" And now a lifetime of guilt and regret greets his mind every morning.
Sexual sins involve other people, and people sin together setting the fires of hell on a two for one! All the more when fueled by lust turning to resentment, rage and revenge. Little sins beget bigger sins, and big sins put people to death.
Some fornication results in a pregnancy and the parents are able to successfully marry and love the child properly. Forgiveness can come easily, a traditional responsible marriage partnership can follow. But rarely do things line up like that. The further from nature one strays, the more destructive will the dalliance be. Not many homosexuals leave their lifestyle and pursue a holy wedded life with a woman.
Sins can be washed away by the Blood of the Savior, but sins' consequences can haunt a man or woman to the last breath.