First few times I had a sitter, though I asked them to sit round the side out of view. Even then the whole experience is not as personal, one does not get the time to reflect afterwards that one would have when alone as nearly always the usual "what was it like what did you see" questions come into play.
I've done it myself to others on occasion, when I know the best thing is to just let them get back to baseline and have a few moments to ponder before banging into an inquisition hehe..
So, once you find your proverbial feet a sitter (imo) becomes a potential distraction, yet still someone you are glad to have there if needed.
I would perhaps say if going alone have someone you can contact, should you need to, should you come back from a particularly heavy and troublesome journey (or even hit up the chat here, I know that has helped a few people before if the right people are about).