The people who say that osas and grace alone allow people to continue in sin also think that we make a decision for Christ. That answering an alter call and saying the magic incantation or sinners prayer makes one saved. So it goes from one misunderstandings to another. Even making a confession of faith is not salvation. What must be understood is believe in your heart. When we sincerely believe in our hearts something it affects our person, our actions and our thinking.
I love to use global warming as an example, all these politicians and celebrities that private jet all around the world lecturing people about global warming do not actually believe their claptrap. If they did it wod affect their thinking and also their actions. People that believe something act on it, not by force of will, but because their belief compels them. I believe in homeopathic medicine, how you know is the herb oils, tinctures and that I pick wild medicinal herbs when I see them. My belief informs my actions. Sunday I picked enough goldenrod flowers to fill a shopping bag, and a heap of asiatic day flower, and right now they are curing into oils and medicines. I don't go out into a field a say oh if I believe this I must do this. I believe it so it informs my actions.
The same way with Christ, I believe Jesus therefore I repent of my sin, and study his words and look forward to his return, because this belief informs my actions. Not the other way around.