Control your eyes to control your attention. The most natural part of your attention to give away freely is that of your vision—it only takes a tiny movement in your eye to cast your gaze from one side of the world to the other. Demonstrate the discipline of attention even in the smallest of details, such as where you look. If someone walks onto the train, don’t divert your gaze from your book. Continue with your work as if nothing happened. It’s unnatural, challenging, but will help you exercise self-control.