For the first class, he had us go out and buy a piece of fruit. I bought an apple for fifty cents. Then we painted. I'm pretty happy with how the first one turned out. It was more careful than the second. In the second one, I just wanted to experiment with how wet I could make the paper and still end up with something I liked. I didn't stop until the instructor started whispering, "Stop!" to me, but I probably should have stopped even earlier.
The most challenging thing about watercolor for me is going to be knowing when to stop. One thing I like (or at least, am accustomed to) with acrylics is that I can just keep painting and painting. It will be difficult, because I won't always feel like putting down the paintbrush, but learning restraint will certainly be beneficial.