Insight meditation - the type that has it's roots in Buddhism - has recently become well-known in the Western mainstream. It is recognized mainly as an empirically backed stress-reduction technique, but it is so much more than that. Not only is relaxation and less stress a side effect of mediating, but it can help to slow down repetitive thoughts enough to understand and gain some necessary distance from them. The basic message of insight meditation is: 'allow whatever arises, don't push it away or try to hold onto it, simply nod to it like you would to someone you are used to passing on the street.'
The reality is that we are accustomed to have many thoughts that are repetitive, some can be debilitating and negative. The ability to slow down those thoughts and question their validity is a basic tenet of both insight meditation as well as aspects of Cognitive-Behavioral Therapy.
The practice of insight meditation is to allow whatever experience is there to pass through your awareness, or even hang out for a bit if it wants to. Simply noticing these thoughts and feelings leads you to begin to understand yourself a whole lot better. It helps to develop the capacity to gain some objectivity by witnessing the thoughts and thereby choosing which you would like to cultivate and believe, and which you would rather set aside.
To understand your thoughts for what they are means that you begin to know them - often swirling judgements, plans, memories, fears, etc, going around and around. When we are "identified" with those thoughts, whatever they are, we naturally believe them. So if you have a recurring judgement about yourself or a chronic expectation of yourself in relationship to others, then you naturally believe it without even noticing that the thought occurred. You end up feeling sad or scared, without understanding that the feeling most likely came from a negative, judgmental, or worrisome thought.
When you start to slow down the process of thought and become more of an objective observer of it, then you can begin to see that your thoughts don't define you. They are often not even based on reality, but are just subtle messages that you may have picked up from relatives, teachers, friends, etc. When you begin to separate from the thoughts and gain some objectivity, you realize that the resulting feelings also change. In other words, why be sad, fearful, or depressed when you are not believing negative thoughts about yourself? Insight meditation can help you to become your own therapist by learning to gain more awareness and thereby control over your mind. What a relief!
For more on Insight meditation, here's a great user friendly book I highly recommend by Jon Kabat-Zinn: Review - Wherever You Go There You Are
Katharina Sandizell, LMFT