[stupified]

It just happened to me when I used to drive with my sister because her driving su*ks. And when I drive, she is always watching me (I dont know if she does that to learn or to look for mistakes but it freaks me out and makes me nervous).
It's all because you are afraid passengers would say something if you screwed up on traffic, they make you lose concentration. Or if someone keeps telling you you are a bad driver as you are driving, you just wanna kick 'em out of the car, or maybe keep em in and scare them a little. You must have at least self-confidence, no stress, and make sure you stay safe. You will do great I am sure.