In Galatians the Bible tells us not to grow weary in doing good.  The reason we are told that, is that it is SO easy to grow weary in doing good.  You do the right things, you treat people according to your guiding ethic of love, and you take a beating for it!  I know that I always hope that when I treat people kindly even when they have been mean to me, that I always hope that God will use that to change their hearts and make the want to be nice and loving in return.  It rarely happens.  It would be so easy to say that I'm done being a nice guy, because nice guys finish last; time to kick some butt! 
But that would be losing heart.  If we can hold out, we will eventually reap what we sow; weather good or bad.  God is a God of justice, in the end, good will be rewarded, evil will be defeated.  Just not now.
The trick is to keep focused on the fact that this is a "long term investment"; eventually we reap our reward; not now.  If we can keep that in mind, and know that our reward comes from God alone, then perhaps, even though it is hard, we can hang on and not grow weary in doing good.