It's easier than it sounds. One of the major problems you usually run into when learning to juggle is that you throw the balls too far forward (their arc should be basically parallel to your shoulders, but it's easy to accidentally give them some forward momentum too), which pulls you forward to catch them. Being allowed to walk means that's OK.
(For the curious, there are three major problems you're likely to have when first learning to juggle:
1. I can throw the balls, but instead of catching them, I let them fall on the ground.
2. My balls keep colliding with one another in midair.
3. I keep throwing the balls too far forward.)
There's actually a niche hobby called "joggling" which, as the name implies, involves juggling while jogging.
A lot of C developers tend to assume the compiler is a dumb program ;) There are significant hoisting and vectorization optimizations that signed overflow can unlock, but they can't always be applied.
Compiler writers tend to assume the processor is a dumb machine. But modern ones aren't, they do a lot of resource allocation and optimization on the fly. And they do it in hardware in real time.