Here are some ideas to help you relax when you begin to feel stressed or upset.  It is important to remember that as our body tightens up and we become tense we cannot think clearly either so this exercise can assist us in gaining control over our body.

Seat yourself in a comfortable position in a quiet room. Tighten up each muscle group to the count of 10 and then relax that muscle group until the count of 10. For each muscle group notice the difference between the feeling of the tension and the feeling of the relaxation. Think of it as a balloon slowly leaking air and collapsing or a flower bud opening and folding back.
 

     1. Tense and slowly relax your fists and forearms.
     2. Bend your elbows and tense and relax your
         biceps.
     3. Straighten your arms and tense and relax your
         triceps.
     4. Wrinkle up and relax your forehead.
     5. Clench and relax your jaw.
     6. Shrug and relax your shoulders.
     7. Fill your lungs and let air out slowly.
     8. Pull in and relax your stomach.
     9. Push down your feet to tense and relax your
         thighs.
   10. Tip up your toes to tense and relax your shins.
   11. Raise your heels to tense and relax your calves.

This whole procedure should take about twenty minutes the first time. Later, it will take much less time. Eventually, you will be able to put your body in a state of complete relaxation at will.

Relaxation Techniques #2
I received this technique in the Hospital and found it very helpful to me. I hope you will find it as helpful.

You must do it a few times and then it really seems to work. Please feel free to print this out.

Grounding Technique:
(Relaxation Exercise)

1. Sit on a chair.

2. Place both feet flat on the floor.

3. Hands around the arm rests. (gripping them gently)

4. Place your back flat against the chair.

5. Keep your eyes open and focus on a spot infront of you, at eye level.

6. Do not look at ceiling or floor.

7. Breathe in - pause - breathe out - pause - (slowly and evenlyy)

8. Now, say out loud (if possible - if not - then say in your mind):
"I see 5 things ..." ( i.e. the wall, window etc..)

9."I hear 5 things ..." (i.e. radio, footsteps, etc..)

10."I feel 5 things..." (i.e. my fingers clenching, the chair, my toes, etc.)

11. Continue Exercise by saying " I see... I hear...I feel... 4 things then 3, 2, 1,".

Then you should be fully aware of your surroundings,  and calmer. Your panic should be a lot less to possibly nil, depending on your concentration.:)