The old saying is "cats have 9 lives." It is not really based upon any actual science, but mere observation that cats tend to get in and out of trouble in McGuffin fashion. For some reason, cats that fall off building ledges always land on their paws.
What if people had this cat-like trait?
We clearly saw Patchy, the one-eyed Other, "die" numerous times only to come back and thwart the Losties plans. That seems to be an obvious writer's ploy to surprise the viewers, and add the taint of mystery about the island (why do some people die, and some do not?) Ben was taken to the temple and was "reborn," but Sayid was taken to the temple waters - - - died and was reincarnated as an evil minion. Locke "survived" a 10 story plunge, an airplane crash, and being shot in gut. Pretty darn lucky; 9 lives cat lucky.
Like most things in LOST, story continuity and rules are very inconsistent. Who lives and who dies is probably more attached to the emotional viewer meter than anything else.
But if life teaches us, everyone comes across events that could change their path, for good or ill. Just like in Monopoly, some people tend to get more "Get Out of Jail Free" cards than other people.
But to put a more sci-fi spin on this concept, one could look at a person's life as having one of those sub-sandwich shop customer loyalty cards: after 9 meals, you get one free. But in the scope of one's life line, the card allows 9 critical events to pass that does not cost you your life. The grim reaper clicks off those events until you run out of freebies - - - then you have to pass on.
You can reflect on your own life to remember various events that could have gone badly.
One probably does not realize that this is happening. But a few, like Patchy, who did crazy stupid and clearly suicidal things, probably did know that he would return. With that type of knowledge, one would have great power to control any situation.
You can count on your own how many of the main characters survived car crashes, mental illness, alcohol /drug addictions, shootings, falls, explosions, fights - - - before, during and after their island dangers.
If you look at the characters as counting down not time, but their 9 lives in order to get to the promised land, then that may explain the dull attitude and lack of grasping their dangerous surroundings when they flew off into the jungle on crazy missions. Their subconscious must have been pulling them through the gateway of their own existence.