Hi Maggi, welcome to the forum. Yes, I know just how you feel. If you're unhappy in your job you feel like the last thing you want is to be rejected for another position. So you avoid going for it. I've done that quite recently. I've even thought 'better the devil you know than one you don't'.
What I've realised recently though is that it's the problems of the job I'm in that's causing this anxiety and fear of trying. So, not only am I unsatisfied in my job, the very thing I want to escape is stopping me escaping it. The will is there, as it must be with you if you are applying, but the confidence is not, because of the present job.
So, I think the thing is to see the fear for what it is, and try not to associate it with the job you're applying for. You might be exactly what they are looking for, and be successful. You don't know until you try. And even just trying is taking action, taking control over the situation you're in with your present job.
I really hope you go for the interview. Here's a tip - spend some time beforehand writing down all the reasons you want the new job - things that are particular to THAT job. Don't dwell on the reasons you want to leave the one you're in. What, other than making a fresh start, appeals to you about the job you're applying for?
Picture yourself doing the job, picture using your skills, being successful in it and using every bit of your experience and knowledge. This will help you give off a positive vibe at interview. And employers do often sense the vibes. They will feel it if you're focused on escaping. Try very hard to focus on what you could achieve for them in the new position, by using your skills. If they ask why you want the job, don't mention your present one - just say why you would be good for them.
You can do it mate. You've got an interview - it's often hard to get that far, so you've impressed them to a certain extent already. Make them feel good about their decision to interview you. Because interviews are actually not all about you, they are as much about the person or people interviewing you - let them see how you could be good for them.
Go for it.
