There is plenty of advice available online that covers various anti-anxiety techniques you can use on the day of the interview - breathing exercises, mental imagery, visualization - so use whichever appeals to you. Remember too that you will be judged on how you appear as well as on what you say, so make sure you practice both standing and sitting with an upright, relaxed and open posture which radiates confidence and self-assurance. 

Make sure you leave nothing to chance. The night before the interview, get everything prepared and ready to go the next day, even if your interview isn’t till later in the day. Choose your clothing, shoes and accessories and lay everything out, along with whatever paperwork you need to take with you, and of course make sure you know where your car keys are. Make sure your car is not low on gas. If you’ll be using a GPS to find the job location, program in the address in advance, and check your maps are updated and loading correctly. Try to get a good night's sleep and set your alarm to allow yourself plenty of time to get ready in the morning.

Exercise can be a good way to quell feelings of nervousness, so - if you feel up to it - get up early enough to exercise in whatever manner you most enjoy. Exercising not only burns off any negative energy but it also produces endorphins, which interact with the receptors in your brain to induce a feeling of positivity and well-being. Make sure you leave yourself plenty of time afterwards to take a shower and get yourself ready to look your very best for the interview.

It is important to bear in mind that, no matter how desperately you want the job, your entire future does not depend on it. It is an opportunity but not your only one, no matter how much it may seem that way at the time.