There comes a time in everyone's life, where they have to ask themselves if their life is as valuable to them as the one they love's would be in a life and death situation.
I don't think most people are comfortable enough with themselves to answer yes to that question Though that raises another inquiry: why are we so willing to think that self-destructively? Why, in such a situation would we jump in front of a bullet aimed at another, but when that same lethal weapon is pointed at us we would gladly take it because we don't think ourselves enough to be able to fight and survive it...
I find it sad - not that I feel enough security in who I am as a person to be one to differ in resolution if put into the same situation - and I don't know where that sort of thing started. The earliest I could really reference would be the Romeo and Juliet days, or Catherine and Heathcliff days... a loved one dies, and so the other ends their life. Though this reference is fictional, does it not show how the people of that time would have been?
I digress...