Speaking out of vengeance just to hurt someone in some way means you have to embellish the truth and create a story that is exaggerated which you must believe yourself. Thus it perpetuates your living in illusions and self-created lies. You cannot find truth in a head filled with lies.
Exercises
Do Not Speak Badly About Anyone
Abstain from any gossip or negative words about any other person. If you can’t say anything good, then don’t say anything at all. Practicing the exercise Do Not Speak While In A Group, will help you learn how to hold yourself back.