He went on to say that he felt "at peace" even during the intense pressure of the tournament. By focusing only on what he could control, and by working hard at it over time, he experienced the positive results. There was less stress, less reactivity, less "thinking and over thinking", less negativity in general. He felt "empowered" and that led directly to "confidence". His "goal pursuit" was therefore calmer and he used less energy.
There is a lesson in that philosophy for all of us. When we focus, too much, on things outside our control we experience the opposite of that list in the paragraph above. This control of our focus is not as easy as it sounds, but the more we practice and make decisions on where we are putting our attention, the more peace of mind and confidence we will enjoy.