For things like the Nav, I think the examiner is looking to see that if you make a mistake, or if things start going wrong for some other reason, that you notice it and take appropriate corrective action. e.g. its OK that you are off-track mid-way through the leg, but its not OK if you don't notice this and don't say so! Talk out loud so he knows what you're thinking the whole time!
Hope this helps, and best of luck mate! Be prepared and all will be well
Andy