I think perhaps the reason people still like the Karate Kid movie so much is that there are bits of wisdom in it. This one from Mr. Miyagi when he was teaching Daniel a hand technique is one of those. Focus here meant to clear your head and concentrate on getting the technique correct.
Last night in class, Sensei Lee used it a different way: he taught focus in terms of fine-pointing your energy, directing it correctly, having the right intensity on it and draining it without letting is dampen. Essentially he was teaching us to deliver a technique efficiently to the opponent: in a direct line with no loss of energy from sloppiness in the delivery. Sloppiness might mean an arm that leaves the chamber during a punch and waivers slightly off path before it meets the target. It might mean not tucking the foot up enough before delivering a back kick. In either case focus is lost, and so is the energy.
As a suitable example, Sensei Lee slapped the Dojo floor with the flat of his foot and simply said: “Splashing energy,” and used his hands to illustrate dispersing energy. He then set his foot down with the same intensity, but this time with the ball of his foot making contact first and said “Focused energy. Give your energy direction.”
“Splashing energy” won’t do the damage that focused energy will. As Sempai Howse said last night, it’s the difference between getting hit with a sheet of paper or nailed with the tip of the pencil.
Focus, efficiency, strength, directed energy, penetration after impact: That’s Shotokan.