I think they're the sorts of machines that are best learned when you're a kid. Somehow my brain had a wonderful ability to help me balance when I was younger that it no longer has. One of my best friends, a guy who's still one of my friends today, and I used to also play "balance beam" and cross over a raging, deep creek by balance-walking along a 4-inch drain pipe that spanned the creek behind our school. We did that hundreds of times, and if we'd fallen, we'd have likely been killed. But we never even worried about it. I couldn't anymore do that now than I could walk on the moon.

I tried juggling when I was riding the unicycle once, but I fell hard on my butt. And when you're riding a unicycle, those falls happen a lot even when you're not juggling.