From Tony Ramos’ Facebook stream:

Amateurs practice until they get it right. Professionals practice until they can’t get it wrong.

Nicely compliments the two Principles of Presentation Disaster Avoidance devoted to practice:

Number 3: If you practice like it’s the real thing, the real thing will seem like a practice.

Number 9: Everyone knows that it’s essential to rehearse, but not everyone knows how to rehearse what’s essential.