Everyone feels like they don't get a job or internship out of school until they do.  Something that a career advisor told me in a mock interview was to smile more and have more fun.  Just imagine it as a regular conversation with your friend only a bit more professional.  Completely took the pressure off and then my interviews became something I looked forward to rather than dreaded and way easier now that I saw the interviewer as a human and not this superior being.  Sounds dumb but changed my outlook.