One of the most insightful (at least for me) biblical stories is found in the Gospel of Matthew, and deals with Christ at the Garden of Gethsemane. In case you are not overly familiar with the story, it takes place the day before the Crucifixion of Christ. The details aren't so important to this discussion, other than Christ goes to this garden to pray, knowing that he would be betrayed by Judas, turned over to the Romans, and ultimately put to death.
Now what's so insightful about that?
Consider This: According to Christian teaching, Christ...being God...knew that by going to Gethsemane he would ultimately be put to death. At any point he could have changed his path and spared his own life, but he chose not to. He consciously sacrificed his own life, if you believe in Christian teaching, for the greater good of all mankind.
Consider This: To this day, people make conscious choices that ultimately lead to their death. For example, Father Mychal F. Judge, a Franciscan priest, went into the south tower of the World Trade Center after it had been hit by an airplane to minister to the wounded. While history doesn't record whether or not he thought he would die, it's pretty clear he knew what he was doing was exceptionally dangerous.
In the final analysis, some of us will be faced with our own "Garden of Gethsemane", where we need to make a choice between self-preservation or preservation of the greater good. Ultimately that is the most personal of decisions that anyone can make, and furthermore I doubt any of us are prospectively capable of saying what we would do if put into that situation. There is, however, no greater love that can ever be expressed than through the thoughtful and conscious act of sacrificing oneself for the greater good.