Ok, so the truth be told, a lot of time when you attend an interview.. you feel it's out of your control, get nervous etc. The secret is simple....
You are always in control, when you get invited to an interview, always remember it's a two way meeting. Not only did you apply for the role, they invited you for an interview because there is something about you that they want to see in person rather than on paper.
Always remember, you're in control, it is your decision at the end of it all (except in some cases of course when your choices are limited.)
Always show your personality in an interview as that helps the interviewer know if you fit into their company culture. If you do not get chosen for the position, remember you may have dodged a bullet and they have done you a favour!