There are people we forget easily. They come into our lives for minutes or hours or days, weeks, months, even years, and, when gone, still are forgotten as easily as the things at the grocery store that we constantly forget to pick up. Just because these people are forgettable, it doesn't mean that they were never close to us. And perhaps 'forget' is too strong--they aren't forgotten in the way that one forgets a fact. In truth, they simply slip our minds. Our lives move through phases. Friendships, even strong ones, wax, wane, ebb, and flow.
Of course, there are also people we cannot forget. For whatever reason--be it some love or some hurt, some deeply felt moment that was shared--they are constantly at the back of our minds. Images, sounds, touches of memory return at the slightest provocation: a street sign, the old house, another little brown car, old emails, old jokes. It doesn't seem to matter how much we try to put them away or marginalize their absence, they will not be forgotten. These people who will not leave our minds are always associated with our deepest emotions so that the street sign or that sound, though innocent of any intention, might call up fears and hopes that resonate with our hearts and souls.
It is this deep emotion that makes them so hard to forget. To ignore or forget the person is to ignore or forget, to marginalize, emotions that are the core of our present being. Those emotions represent the moments that we felt most alive. They are often also the moments in which we least wanted to live. But whatever emotions belong to those moments, they are the context in which we feel and live today--they are the moments by which all others are measured.