Think about this situation... you created a presentation for a meeting. During the meeting some of the other people question you in what seems like an attacking way. After the meeting you think about, what could you have said? What should you have presented? Maybe you do not know the subject as much as you think you did? What should you have said to them in the moment? You go home, and along your drive you are still thinking about it. You try and forget it so that you can watch a show with loved ones, or eat dinner with your family, but you are still thinking about it. You go to bed, but you are still thinking about it. This, is rumination. Rumination is any situation where you replay an event repeatedly in your mind, mulling it over and over.