Hi Wanda,
The way I stop and prevent a racing pulse is by not fearing it. Easier said than done, I know. The trick is to have something to focuss in on to replace focussing in on the panic. Are you doing the Panic Program here on the site? Highly recommend you do, theres some wonderful relaxation tips to learn. One of them is 'box breathing'. This has helped me a lot. What you do is slow your breathing down to a steady pace. When you inhale, hold it for about 3 seconds, then exhale and hold it for 3 seconds. Do this lying down and place your hands on your stomach. You'll know you're breathing correctly when you feel your hands moving up and down with your stomach. At first you'll probably feel more anxious as you hold and count to three. I do, but stick at it because it's really good for slowing down both your thoughts and your pulse. Oh and watch you don't take huge breaths. Just do it at a steady pace and try to keep your breathing natural.
Hope this helps. :)