According to those who believe in the bible it's written, "For god so loved the world he gave his only begotten son"
This would lead one to believe that love is worth sacraficing a life for. However I'm incline to believe that love is worth living for.
With regard to an eye for an eye.
I think seeking revenge is an instinctive thing to want to do.
However it's not always the best approach to take.
If two people are stubborn and determined to avenge each hurt the other inflicts after a while they will have lost sight of what is really important. Thus an eye for an eye makes the world blind.
Sometimes the best revenge is to move on to bigger and better things.