Great music starts long before it is ever heard. It is prepared inwardly well before any notes are sounded. It doesn't just happen if we're lucky, or materialize out of a vacuum. Something must first be brewing and stirring inside the musician, composer, performer. That is what is going to determine what kind of product will be produced. Something has to be actively wrestled with before the product is ready for performance.
The challenge that is ever before us is to maintain the quality and quantity of musical input that feeds the output. The reservoir must stay filled. Talent alone will not match the requirements over time. Talent, good instincts plus a steady diet of great music and the practice of it will work. Call it the ability to maintain motivation, the drive to express what is passionately felt, and the perseverance to refine it all for future performances.