If people don't recognize their own need for rescue then they won't be willing to accept your help. They might politely listen to what you have to say, but when the conversation (or sermon) is over they will simply move on with the routine of life. It is a frustrating situation to share the truth that will save someone when they refuse to acknowledge that they need it. I know that their response does not hinge on the persuasiveness of our speech. It doesn't negate the frustration that you feel when you can see how desperately someone needs God's intervention and yet how unwilling they are to see the need for His truth. Our job as Christ followers is to be faithful in sharing God's impact in our lives while praying for receptivity from those we interact with.
We can't make anyone seek rescue from drowning, but that doesn't mean we have the right to stop offering the life preserver either.