Hi ANewDay, this is a great question. There's many ways to release emotional pain, though in my experience, many take time to have an effect, or I simply haven't been effective or any good at all at implementing them. There are two methods I've found which have an immediate impact however, that have helped me in the past to create almost instant calm.
The first is exercise, though may not be applicable here, unless you intend to sprint into the interview room in your interview outfit and start busting out squats and starjumps on the table
The second is one I feel may ideally be for you in this situation. I discovered it when I was younger, prior to falling into full alcoholism, and used it often to achieve a calm and almost serene effect, although in my case, I used it from time to time to calm my nerves before a date, haha. I believe it'll be just as effective prior to a job interview though.
It's called 'tapping', or 'EFT therapy' (from memory, the EFT stands for 'Emotional Free Tapping' or 'Emotional Freedom Technique'). It basically involves you sitting down (It can be anywhere, though preferably private and quiet, I would often do it in front of my laptop), and physically tapping various acupuncture pressure points whilst repeating certain phrases.
Now I'll admit straight away that it can feel silly and ridiculous to sit there tapping your body whilst repeating mantras, that is until I was through with my first 20 minute session - it worked! I couldn't believe it, went on my date with a cool and calm serenity, and was able to be myself in a way I might not have been if I was a bundle of nerves.
I think the method has gained traction over the last couple of years, because it has started popping up all over the place. There are even EFT specialist therapy sessions you can go to, but those can cost up to hundreds of dollars for a single 1 hour session. I don't understand why you'd pay that much for something that is so easy and that you can do in your own home (or anywhere), which doesn't actually take anywhere near 1 hour in my experience. I've just looked it up on YouTube, and there seems to be a guy called Brad Yates who seems to be proficient at it (I haven't watched his entire videos though, so have a look around).
Simply type in 'EFT therapy' into Google, or maybe 'Brad Yates Tapping' into YouTube, and you should be on your way.
Like I said, it may feel silly, but give it a go once and see how you feel. Let me know!
Cheers,
Seb.