As my guitar teacher used to say, “Slow is fast”. Mastering the techniques slowly and increasing speed until you’re “at speed” is the way to go.
Like riding a bike, you start slow with training wheels (or a helicopter parent) and work your way up to Yolo no-hander off that kicker ramp at 40 kph.
Shame you can't do this with something like juggling. :D
I suppose you can somewhat metaphorically replace speed with numbers there. In that juggling four balls is a lot like three, but faster. Getting the initial three going, though... Grrr.
Ironically, training wheels are actually a bad way to teach a kid how to ride a bike. They teach kids bad habits (like turning the handlebars to steer rather than leaning).
Balance bikes are a better first step and are actually really fun compared to training wheels.