Nothing. Human lives are equal, but if you have the chance to save many by sacrificing one, the choice is obvious. Our ends are in some ways inevitable. We're all going to go sometime, be it in a glorious final battle at the side of... at the side of those we love, or alone in the dust of some unknown world. There isn't an easy answer to your question fo why, other than you were in the time, and at the place you needed to be. You made your choice, and accepted what was before you. It takes courage and honor to do that.