You will be more relaxed in the interview if you have aligned your passions with what they are looking for. Your confidence from this alignment will help create your relaxed posture. Body language speaks volumes without ever saying a word so coming in with this confidence will quickly be seen AND felt by the interviewer and makes you more likely to be remembered by them. The opposite is true also, being uptight and anxious because you are not confident will quickly be felt by the interviewer and will most likely be a detriment. Remember; go for relaxed, confident and calm. Avoid doing things like: tapping your hands or feet nervously, being too anxious to talk, or crossing your arms which could indicate you are closed off to communication, all of which give the message that you might not be a good fit.