If it makes you feel any better, your description of your first two days sounds exactly like how I felt when I started my summer job last year. It was the first full-time job I had in the "real world" in which I had no familiar people or environment. I even remember telling Sean after my second or third day that I didn't think I would *ever* get the hang of it, and that they would have to hire someone else.

Obviously, my prediction was made a little prematurely. :P Everyone knows that you're starting out, so of course they'll expect questions and mistakes as you learn the ropes. Of course you're smart and you'll learn it all. Also, I think you'll adjust to the monotony of a full-time work schedule, so you'll have some more energy in the evenings. Plus there will be those deliciously free weekends!