Sherlock knew more about the solar system than he usually let on. He knew that the Earth revolved around the Sun, and the Moon around the Earth itself.
He knew that that was the way it was always going to be with the two people that mattered the most to him. John was the Earth and Mary was the Moon, it was only natural that she eclipsed the Sun sometimes.
And even if he could swear his whole world revolved around John rather than the other way round, it didn't actually matter. Their complex dance was never going to stop.