Sounds like you had a great first day!
I too, (and still sometimes) flop around like an idiot. My first run was very similar to Eats'... my friend took me on a steep blue (well as steep as you can get in Ontario lol), icy run and though I was gonna die. I made it down like 10 mins later, after falling so much on my butt doing "the falling leaf"... fun times hehe.
Remember to always stretch before you start boarding and after a day on the slopes, get in a hot tob if you can (hot bath or shower will be just as good) and apply ice to swollen areas if any, or I like using Rub A535.