Newbie - FAQ
After some mutual back and forth on schedules, I finally was about to see a well-reviewed provider. (I'm a relative newbie and more of a once-in-a-while-in-between-girlfriends guy.) In anticipation of her lauded DFK skills, I decided to shave the shortly cropped beard I've been wearing for the last six months. Nothing like a make-out session with a freshly shaved face. 
A couple hours before the meetup, I shaved, felt great, but then noticed that I had a small canker sore in the corner of my mouth. Never had a fever blister or cold sore, so I know it wasn't that, just a tiny red spot. Probably invisible to anyone else, but I knew it was there and it gave me pause both for *my* safety and the provider's.
I wasn't planning on doing any DATY as I'm very cautious and like to play it as safe as possible. But as I was really into the idea of making out with a very cute girl, I began to think this might be an issue to be concerned about. I finally texted her and cancelled the session, regretting it every step of the way. She was totally cool and seemed into the idea of meeting at another time, even though I didn't disclose the reason I was bailing (which began to seem silly).
So... as my subject line reads: overly cautious? or did I do the right thing?
I always prefer a gentleman cancel if he's not entirely comfortable -- even if it seems like it's for something silly.
I've had plenty of gentlemen cancel/reschedule for health reasons (true or perceived), and I've also done so myself. I think it's the respectful thing to do, particularly when it might be contagious -- or even just *look* contagious. When someone cancels a date because of a health concern, that earns them nothing but brownie points in my eyes. I appreciate that they're looking out for my health too, and I want them to feel their best when we meet. They'll need the energy. 
Now, if you get "sick" three times in a row, that's a problem! But once? Not a big deal. The more notice the better, though.