Breathing is one of the easiest and best ways to calm down. Practice proper breathing exercises by inhaling through your nose and exhaling through your mouth. Repeat this until you start to calm down.
Chew gum, especially peppermint gum
Chewing gum is good for relieving stress (before the interview—not during!) and can improve your focus and concentration for the interview. You need to get sugar-free gum, or better yet, use peppermint gum for a more soothing effect.
Less caffeine and sugar
Avoid caffeine and sugar at all costs when you get nervous before an interview. Caffeine and sugar make you go into overdrive; they heighten your nerves and will make you even more agitated.
Eating foods that are high in protein can help keep your blood sugar levels balanced and improve your focus, which is essential in the interview.
Having a proper night’s sleep will make your body and mind refreshed and prepared for the challenges you’ll be facing the next day. Not having enough sleep will reduce your alertness during the interview and can hurt you.
The most important thing is to prepare. With proper preparation, you’ll know you have the right tools to ace the interview. You will have the confidence you need, because you can learn every possible way to calm down, but that will be of little use if you did not prepare for the interview.