There’s an American Indian legend that teaches an important lesson:

A young man came to his grandfather, angry at a friend who had done him an injustice.  Let me tell you a story, said the grandfather.
I too, at times, have felt great hate for those who have taken so much with no sorrow for what they do.   

But hate wears you down, and does not hurt your enemy.  It is like taking poison and wishing your enemy would die.  I have struggled with these feelings many times.
It is as if there are two wolves inside me.  One is good and does no harm.  He lives in harmony with all around him, and does not take offense when no offense was intended.  He will only fight when it is right to do so, and in the right way.
But the other wolf, ah!  He is full of anger.  The littlest thing will set him into a fit of temper.  He fights everyone, all the time for no reason.  He cannot think because his anger and hate are so great.  It is helpless anger, for his anger will change nothing.
Sometimes it is hard to live with these two wolves inside me for both of them try to dominate my spirit.
The boy looked intently into his grandfather’s eyes and asked, “Which one wins, Grandfather?”
The Grandfather smiled and quietly said, “The one I feed.”

Of course the story is an allegory for the internal conflicts we all have in our lives, good versus evil, right versus wrong, healthy versus unhealthy, positive versus negative.

The legend reminds us that the side of the conflict that wins is the one we give the most attention to.  Feeding the bad wolf may seem justified, but your enemy is indifferent to your hatred and you are the one who is hurt by the havoc it causes in your psyche and life.
When we focus on the behaviors and techniques symbolized by the good wolf, we have more success in our lives, more peace and more harmony.  Choosing to focus on the positive rather than the negative draws the best to you.
Remember, the wolf that wins is the one you feed.