I've flown with a particularly nervous passenger on a few occasions with only a few post ppl lessons. I knew he was generally okay in the aircraft if he was busy taking pictures and if I was pointing out things to look at, but one of the trips was to Clacton. It was probably my worst landing ever, including three or four smallish bounces (all done before the footpath) in a C172. Once things had settled down on the ground I looked over expecting to see a pale faced passenger, but he was absolutely fine.
Afterwards he said he wasn't worried because I was so calm. This made me think about one of the guys I'd met at my then flying group who acted so nervously on his pre-flight planning that he made me nervous just being around him! I can see why alot of people wouldn't want to be flown by a pilot that seems nervous.
I've only ever flown with instructors and non-flying passengers. Thinking about it carefully I'm not sure I'd be happy to sit in the back of an aircraft when a newly qualified pilot is flying!