Learn to breathe and relax. When you're stressed or have to do something that makes you anxious (like a job interview or asking for a raise, etc) just relax. How do you do this? Take a big belly breath. Okay...so let's start at the beginning. If you don't know how to take belly breaths, start with this exercise. Lie on the floor on your back. Put something on your stomach. Anything you have handy laying around...a mouthpiece, a kettlebell, whatever. Now take a breath. Do not breathe into your chest. Try to inhale into your belly. Are you doing it right? Is the thing on your stomach going up and down? Try to push the thing on your stomach up as a result of your inhalation...down when you exhale. Now you are doing a belly breath. Repeat this a few times. Get used to the feeling. Sit up and do the belly breath. You can put your finger on your stomach and try to push it out as you inhale. At the top of the inhalation, hold your breath and count to 3. Then exhale and let all the tension and anxiety out with the breath. Repeat 3 times.
When you are out of breath, focus on breathing into you belly and relaxing.