Healthy Worry. Worry is an anxious preoccupation with an anticipated negative event. Worry helps us adapt by directing attention to true problems that once identified can then be addressed. In this way worry is effective in managing the many, real challenges of life.

Unhealthy Worry. For some people the adaptive process of worry breaks down. Their worries no longer motivate effective problem solving and instead they become stuck in thinking about everything that could go wrong. They are plagued with thoughts and images of disastrous outcomes that in reality may never come to be.

Dwelling on the Past. While obsessive worry is focused on future outcomes, rumination is an uncontrolled preoccupation with the past. Rumination is experienced as guilt, regret, anger, over perceived mistakes, losses, slights, actions taken or not taken, opportunities forever lost. Rumination is often accompanied by excessively harsh criticism and the overwhelming belief that if things had only been different then existing and future misery could have been avoided.

 The Damage Done. Worry and rumination intensify and prolong distressing emotional states. Worry reinforces anxious feelings – you literally scare yourself – which, in turn, only leads to more worry. The process can extend into anxious periods lasting hours, days, weeks, even years, at times spiraling into panic attacks and emotional “spikes” of anger, guilt and shame. Rumination reinforces feelings of sadness, hopelessness and anger, and if left unchecked, can sink into depression and withdrawal.

http://cognitive-behavior-therapy.com/obsessive-worry-and-rumination-2/