This is the time to put your best foot forward -- and while what you are saying may be the most eloquent, thoughtful and impactful thing the interviewer may have heard all week, he won't hear it if he's preoccupied with paying attention to your toe tapping, leg swinging, and lip biting. 

Check out this excellent infographic above for more reasons why you should pay attention to your body language during a job interview or any kind of presentation.