Freaking out over job interview

I have a job interview tomorrow for a position I really, really want. The university hospital where I live is one of the top hospitals in the nation and they hire nursing assistants (they provide the training for it so they don't have to be certified to be hired) but I'm just freaking out. I think it's because I want the job so bad and have been applying everywhere it seems and not getting hired for the jobs I really, really want. But this would be an amazing career opportunity and better my life so much...I just don't want to get my hopes up too much. I'm surprised they even called me at all since it's super hard to get hired there but then again maybe they just interview everybody like most places do. I'm just being really hard on myself. I don't have the fanciest or nicest interview clothes or money to buy anything new before tomorrow otherwise and I think that's what's really discouraging me too. Could everyone please say a prayer for me if you're into that kind of thing. I'd really appreciate it. :/