Distraction can be a major problem at my current RC club here in Japan. It seems to be part of the club culture that people stand around next to you and talk to you while you fly -- and this means they're talking to me in Japanese! In the past this has cut both ways in that at least once the guys have really saved my bacon by pointing out something relevant for example that the sound of the engine isn't quite right or that it looks like I might go into the trees and need to pull up or the advice I got on what to do the time my carb got jammed at full throttle.

But all it takes is an moment of "lost focus" and you can get turned around in the air. I think the comment about making sure you are mentally AHEAD of the model is a very good point.