To turn against another person is to turn against yourself.  To hurt another is to hurt yourself.  To hate another is to poison your own soul.  You are meant for community.  It matters how you interact with your fellow humans.  It matters in what you become.  You are shaped in ungodly ways by ungodly actions.  Likewise, you are being shaped like Jesus by Christlike actions.  Your deeds can be a means of grace to yourself and others.  If your deeds are evil then it robs you of your very life.

“So are the ways of everyone who gains by violence; It takes away the life of its possessors.” Proverbs 1:19 (NASB)