It's difficult to say which breathng exercises are suitable for you given the limited information. All the suggestions above are great for starters. However, one of the shortcomings of deep relaxation or conventional breathing exercises is that it doesn't address the cognitive aspect of anxiety or panic symptoms. While you're engaging in these breathing techniques, your mind could potentially still be saying "Oh no! This is not getting better!" or "When will it stop?" The thoughts may still be there which could exacerbate your anxiety.
Mindfulness meditation incorporates both a cognitive and physiological component to addressing anxiety or stressful situations which could cause anxiety. Obviously, with all exercises - practice is required. Mindfulness meditation-based stress reduction has shown to have long-term beneficial effects on the treatment of people diagnosed with anxiety disorders (Fletcher, Kabat-Zinn & Fletcher, 1995).
Here's a short summarised exercise called the 'Three-Minute Breathing Space' if you want to give it a short (Segal, Williams & Teasdale, 2002):
Sit with the soles of your feet touching the ground and your back upright yet supported and comfortable, in a dignified and erect yet relaxed manner. Allow your eyes to close or, if you prefer, just allow your eyelids to relax as you cast your gaze gently at the floor. Focus your attention to the soles of your feet and then to the flow of experience that unfolds in your mind. Observing thoughts, feelings, and physical sensations, allow yourself to just notice, as much as you can, what presents itself to you at this moment, paying particular attention to those feelings, ideas, and sensations that may be unpleasant or upsetting. Don't try to push them away, allow them to be just as they are.
Next, observe your breathing ad direct your attention to the movements within your body as you exhale and inhale. Take this minute to simply follow the breath and its movements. There's no need to judge or control your breathing, just watch the breath.
Next, allow the scope of your awareness to widen to gradually encompass your entire body. Sense as if your body is expandin as you inhale and as you exhale, completely let go of that awareness. Stay with this experience for about a minute, letting your mind and body open Up as best as you can.
When you're ready, direct your attention again to the soles of your feet, then to the top of your head, then to everything in between. Open your eyes and then let go of this exercise entirely.
Hope this helps.
- Fletcher, K., Kabat-Zinn, J. & Miller, J. (1995). Three-year follow-up and clinical implications of a mindfulness meditation-based stress reduction intervention in the treatment of anxiety disorders, General Hospital Psychiatry. Volume 17, Issue 3, May 1995, Pages 192–200.
- Exercise originally adapted from the MBCT protocol, cf., Segal, Z. V., Williams, J.M.G., & Teasdale, J.D., Mindfulness-Based Cognitive Therapy for Depression: A New Approach to Preventing Relapse (New York: Guilford Press, 2002).