Thoughts in the brain come from the left (past) and right (future) constantly. There is almost no way to stop them, as they are innate part of human existence. Spiritual masters who know meditation are able to soothe their left and right channels and stay on the central channel, which results in these thoughts from past/future subsiding.
Eventually the person is able to experience freedom from these annoyances. Check out the references below for more info. Or try a simple meditation exercise here: Meditation Basic Excercise