Every time you find negative things to post about someone, you become a troll. You may frame it as negative criticism to better the other person but you know that deep down inside you want to upset the other person. A person who has no good thing to look forward to in their life will want to make others as miserable as he is.
To get away from this behavior, you have to look for something that gives you pleasure in your life. When you find contentment in your life, you will not want to take away other people’s happiness. Every time you feel the desire to tear someone’s life down, ask yourself why you are so happy to bring another person to the dumps. Is it likely that you are in that place yourself?