A few things:

I mostly ride on flat trails. I checked out a new one today. This one has hills. One of these is really steep, then there's a less-steep section until you get to the top. I managed to get two-thirds of the way up the steep section before I had to get off. I turned back at that point. I didn't want to have to be picked up when I only had a vague idea of where I was. (My mom also has no sense of direction.) Guess I need more hill practice!

Related to my turning-around, I managed to descend this particular hill with only minimal freaking out and didn't wipe out on the corners!

I also discovered that I can now ride hands free for about two seconds, and can grab my water bottle and even drink from it. I can't, however, put it back! This discovery resulted in another one--what that plastic loop is for. Clearly, it's for holding your water bottle between your teeth so you have your hands free to brake, allowing you to stop and put the bottle back in the cage.