Having a sister or a friend is like sitting at night in a lighted house. Those outside can watch you if they want, but you need not see them. You simply say, "Here are the perimeters of our attention. If you prowl around under the windows till the crickets go silent, we will pull the shades. If you wish us to suffer your envious curiosity, you must permit us not to notice it." Anyone with one solid human bond is that smug, and it is the smugness as much as the comfort and safety that lonely people covet and admire.