Most people who try to kill another don't know each other very well thus they don't know what they actually have in common.
Think about this
If you take two men who have tried to kill each other and stick them together in solitary confinement, (two separate cells next to each other) where they only have each other to talk to and communicate with, they will find out how much they actually have in common and theoretically could become very good friends.
After a period of a few months, you could stick these same two people in the same cell and the likeliness of the desire to kill each other would have almost dissipated if not completely.
When you take enemies and allow them to talk without any outside influences, pressures or prejudices they begin to tear down the walls of separation and it's not too long and they'll wonder why they were ever enemies in the first place.
I don't see self preservation as an honorable trait in humankind because we are only trying to preserve something that is of the physical world and cannot be preserved. The less we are aware of our spiritual essence, the more we will lean towards self preservation because our self is known to us as our body and the things we have. We should have big jars where we can put dead bodies in and fill them with formaldehyde or pickling juice and then we can call it self preservation.
If the jars are big enough we could include jewelry, money, cars, homes and all those silly things we humans place our identity within.