Well, I got the job!
My boss is starting me off slowly so that I can build up clientele; this is good because I can work up to full time rather than jumping in the deep end.
My anxiety is through the roof. Last night I rocked for about an hour and tapped on my head until I saw stars, but I was able to calm down after a while. (Deep breathing and muscle relaxation techniques.)
I find I am paranoid that I will make a mistake, but I think this will get better as I become more familiar with the environments and routine.
I really enjoy my time with the animals, though. So I'm going to keep focusing on that.