Stress often causes us to breathe shallowly and this almost always causes increased stress. Mentally scan your body for physical tension. Does your chest feel tight?
If so, you may be holding your breath without even knowing it. Shallow breathing puts less oxygen into the blood stream, producing an increase in muscle tension. When you experience headaches or feel anxious and uptight, try this:

• Choose a comfortable place to sit, preferably away from other people. Sit up straight and keep your feet flat on the floor. Imagine and feel your feet being rooted and connected to the earth.
  
• Place your hand on your chest. Place the other hand at your middle Dan Tian, one of your body's three reservoirs of energy centered at the middle of the chest.
  
• Begin taking slow, deep belly breaths. Concentrate on your body expanding and contracting. Visualize your energy sinking lower and lower into your body. Continue this breathing exercise for one to three minutes or a minimum of ten sets.  Breathing into the lower Dan Tian (below the naval) helps release fear and anxiety. In doing so, you create additional stability, and become more centered and secure within yourself and your body.