The original quote goes “If you have to ask what jazz is you’ll never know meaning”, and I don’t think it was to be taken too literal. I suppose it refers to not being able to feel what jazz is, or in this case, not being able to feel what juggling is.
Anyway, enough off topic.
I had another thought on the perfection:
Maybe perfect juggling is juggling that goes precisely according to plan, whether the plan is to “improvise”, “create new moves” or “land a trick”. The perfect juggler could be the best possible person to perform for an audience depending of the needs of the audience. When the audience is you yourself, you are probably the best juggler to entertain yourself, which makes me very happy about my own training. Nobody could do my own training better than me, therefor I’m perfect!