The point of practicing is to fine-tune the body so it will respond to the demands of the mind. Technique should never be the sole pursuit. You must tap into your musical mind, otherwise your performance will suffer. When I hear a performance that is particularly moving, I know the musicians have been successful in creating and expressing their musical image. You don't sense the effort in what they are doing, only the result.
Musical clarity is the product of well-defined choices.
Call it imagery, visualization, hearing the music first, etc. What you call it is not important, the result is the same. Mental imagery allows the musician to match their performance to the music in their minds. This mental focus seems to transcend mere physical results. A study conducted by the Soviets prior to the 1980 Lake Placid Olympics provided some interesting results.