I like this explanation. I don't think so much about duty, but more about finishing the experiences that they incarnated to have in the first place, though I suppose duty could be one of them. It is sort of like dropping out of life school, you signed up for the classes, but got freaked by the difficulty and quite. So you slap yourself on the forehead and say why did I do that, now I have to start that particular class all over again. Obviously I am simplifying here, but that is the gist of how I look at it. I think if a soul finds it has accomplished what it set out to experience in a given life time and decides to leave, it is more likely to arrange a more natural exit.