They need to understand that you want to be alone at times; like if you wander off, don't come looking for me, that kinda thing. I've failed as a sitter before by being overly protective and others have for me as well. Sure, don't let em wander into traffic, but if they're on a big empty beach and wander away 500 feet, it's no biggie, let them be. Sometimes you just want to be alone.
Also, it's just one of my pet peeves, I hate being asked, "How's your trip going," because it's really a silly question, so personally I would ask my sitter to never ask how I'm doing; if I have any words for them, I'll talk to them first.