If I can just get my foot in the door, I can get the job. This is a common thought as you go through the job search and application process. Getting called for an interview is a big step forward and one you should certainly be proud of, as it means you've gotten further than the majority of candidates. However, an interview is not the end goal of your job search – the job is the end goal.
When you go in for an interview, maintain the mindset that you are still being considered for the job. There is no guarantee that you will go further in the interview process or receive an offer until you actually get one. You should be well prepared and put your best foot forward.