This is “Hate,” a poem by James Stephens.  It has always expressed a strong message to me.

My enemy came nigh,
And I
Stared fiercely in his face.
My lips went writhing back in a grimace,
And stern I watched him with a narrow eye.
Then, as I turned away, my enemy,
That bitter heart and savage, said to me:
     “Some day, when this is past,
     When all the arrows that we have are cast,
     We may ask one another why we hate,
     And fail to find a story to relate.
     It may seem then to us a mystery
     That we should hate each other.”
           &nbs p;           &n bsp;         Thus said he,
And did not turn away,
Waiting to hear what I might have to say,
But I fled quickly, fearing had I stayed
I might have kissed him as I would a maid.