It is a good analogy, but this situation is slightly different to a smoker. We are talking about eternal punishment, not a few years suffering with cancer (despite how bad that can be). I agree with you that there is only so much you can do with someone like a smoker; if they refuse to listen to you, there's not much else you can do, but if it something infinitely worse than getting cancer, like going to hell, you should do EVERYTHING you can to stop that from happening.
Okay, so instead of smoking, a better analogy would be the ring from the Lord of the Rings novels and films. I hope you are familiar with them so you know what I'm saying.
In the story Gollum, Bilbo and Frodo become addicted to the power of a magic ring. The ring is a fitting symbol for the thing our race, and the fallen angels have become addicted to: self.
The feeling of being an individual against or for others, depending upon how they respond back to you, instead of recognising that the self is actually an illusion and that we are all connected, and the proper response towards others is unconditonal love, compassion and affection.
So in the Lord of the Rings, Frodo must destroy the ring lest Sauron get it. If Sauron gets his ring back, it is like all of Middle Earth would succumb to a terrible cancer and die. But Frodo in his heart doesn't really want to destroy the ring. He wants to keep it all for himself. Gandalf and Elrond could easily take the ring from Frodo, but it would ruin him in the process, and then they'd be the ones tempted to keep the ring. All they can do is encourage Frodo and hope that things work out.
Jesus came into the world to teach us that like Frodo, we have a great act to accomplish, otherwise we shall be in the most dire of circumstances. Instead of a ring though, the thing we must surrender is our very self.
Hell is the clinging onto the self, which if left unchecked would be an eternal spiral into unending hurt. A selfish man can do a lot of damage in a lifetime, but an immortal man can do infinite damage.
It is like holding onto your breath: the longer you hold on, the worse it feels. We have to learn to exhale. To give back, and share, instead of wanting to hold what we have forever. The thing we have to breath out is our life. But in a mysterious way, by giving up that life, it comes back to us. By clinging to that life, it dies.
So when it comes to trying to save someone from Hell, the way that person is to be saved is through the surrender of their self. If the person is selfish, they're going to be as obliging as Gollum would be to give up the ring. Even noble Frodo couldn't do it in the end. None of us can do it, that is why Jesus did it for us.
So trying to save people from Hell is a very delicate matter, which is why Christians don't go crazy. Like Gandalf and Elrond, they do what they can, but in the end only the individual can renounce their self.
