A thought comes up reminding you of an important, often troubling issue. It triggers a train of thoughts that gets stronger and stronger as it takes you through scenarios of what you could of or should have said or done or how things can turn out in the future. Your stories repeat themselves over and over again. Emotions are triggered. You are more and more troubled as you try to, but cannot stop the train.
Obsessive thinking is annoying and, when the thoughts are about negative events, stressful. It is restlessness and worry, hindrances to concentration and peace of mind. Obsessive thinking gets in the way of clear thinking. it is a distraction and a waste of energy.