Mindfulness practices can sometimes bring up very strong emotional and physical reactions. Most often, the practice offers a way to "be with them" long enough for them to resolve and/or "pass through", but sometimes they are just too strong to be effectively dealt with using the MBSR practices alone. In these cases, it is often, but not always, unresolved trauma or other extremely difficult experiences in the past that are emerging. It's important to have a way to assess whether this can be dealt with in the context of the MBSR course or whether it's better to stop doing the course and/or get the help of an experienced counselor or therapist.
There are a number of ways that unresolved trauma might express itself during a mindfulness practice, including shaking, trembling, feeling nauseous, suddenly going numb, feeling dissociated, spontaneous images or memories appearing from the past, feelings of panic, or just feeling unaccountably fearful or anxious. If it's possible, don't fight these responses, just let them be and gently return to breath or the audio guidance. Another option is to create a break from the practice (some of these suggestions are on the FAQ page, in the section called, "I have strong emotional (or physical) reactions"). If, after a little while, things settle down and, although you might feel a little "spent", your overall feeling is one of release and relief, then this is a good sign, an indication that previously unresolved trauma is beginning to slowly "bleed off". You may go through this many times, but if things are truly "bleeding off", the reactions will be less and less severe over time. In this case you are, in fact, dissolving, bit by bit, the effects that the past trauma or difficulty has had on your body and mind, through the mindfulness practice.
If, on the other hand, you have this kind of severe reaction nearly every time you do this practice, and you don't feel a sense of release or relief afterwards, and it doesn't seem like it's getting any less severe, you can substitute a different practice such as Yoga 1 or Yoga 2, which are typically less activating. Another option is to take a break from the course altogether until you get some help from a counselor or therapist who is experienced with trauma. Once you start with them, you can either continue with the course with their guidance, or return to the course later, depending on what you and your therapist decide is best. There are two therapeutic approaches which are very helpful in dealing with trauma and have mindfulness at their core: Somatic Experiencing and Sensorimotor Psychotherapy.
If it's not possible to work with a therapist who has experience with these modalities, there are some very good introductory materials that are worth exploring, including this 6-minute video about Somatic Experiencing narrated by its founder, Peter Levine. If you then want to understand more about the experiences you've been having and how they relate to previous trauma, get Peter's book, Waking the Tiger. He also has a short self-help book that includes a CD and offers a gentle, but powerful introduction to this way of working with trauma called Healing Trauma: A Pioneering Program for Restoring the Wisdom of Your Body.
As with everything in this course, it's important that you check in with yourself to see what feels right for you, and not go beyond your own limits into areas that feel unsafe or dangerous. This checking is a mindful practice in itself.
