Or another way of saying the title is that there are two types of technique - mental & physical. The physical side of practicing could basically be compared to weight-lifting - you need a certain minimum physical strength & dexterity in order to to play the instrument - things like finger independence, finger speed, being able to produce a loud sound, proper posture. Those things are incredibly important. The rest is mental. One must first have a concept of what they want something to sound like (whether you do that through visual, textural, aural adjectives/metaphors, doesn't matter - you just have to have some goal) & then the rest of practice becomes about 2 things: trying to create that sound & trying to find the least demanding (most-tension free) way of consistently doing it.
That revelation/realization seems incredibly significant and fundamental to me at this point and addresses progression on any instrument. You can do all the technique in the world, but it has to have a purpose.
One thing I've noticed is that a lot of musicians tend to discount other musicians who can play very fast ... I think this is pointless - it is simply one aspect of technique (and an important one)
On another note, a musician friend recently pointed out to me that English has very little adjectives to describe sound, and consequently, we use a lot of visual imagery - I thought that was an interesting point.
I'd write more, but I think that hits the heart of it, and I'm not feeling so well at the moment...