(Proverbs 27:22 KJV) Though thou shouldest bray a fool in a mortar among wheat with a pestle, yet will not his foolishness depart from him.
Face it. Some people will never learn. At least they will never learn from anything you do to or for them. As a school teacher I find this hard to deal with but it explains a lot when I look at experience. We might quote the proverb, “You can lead a horse to water, but you can’t make him drink.” Some say that you just need to make him thirsty. Those people do not understand the stubborn nature of fools. They know better. They just refuse to admit it.
So? Give it your best shot and move on. Don’t feel guilty if you have lived the life, talked the talk and prayed the prayers. They are not interested. It is ultimately the job of the Holy Spirit to cut through the foolishness.