Oh, for God's sake. I'm afraid when discussing self sacrifice, even real cases become a metaphor.:ultracool
Sean
You can take it to extremes to illustrate the obverse, though.
If self-sacrifice for one's chums is a good thing, when if one should become marooned in a lifeboat, one should immediately look for a way to off oneself, with the idea being that one's pals could have a bit of a picnic on one's edible bits. Yet in cases where the horrible has happened, it seems most have gone rather unwillingly into the stew pot.
If I think about it some, I can probably come up with justification for self-sacrifice in any number of ways. From selling my possessions and giving them all to charity - which Jesus did urge, as I recall - to donating various organs that I possess in duplicate to actually self-destructing to avoid continuing to burden the earth with my various polluting ways.
Nature urges self-preservation, and intelligence urges that self-preservation be balanced with the preservation of the society that supports that to which we have become accustomed and prefer. There is little found in nature that urges self-sacrifice, lemmings to the contrary.