Now I get it.

After nearly a year, after seeing another birthday and living fall, winter, spring and summer once again, I think I finally understand. This isn’t going to go away.

Do you remember the media, right after September 11? Two days, three days later, even that very evening, they were saying how we were all forever changed. But how could they have known, really? How could any of us have known, except those who lost people who were dear to them?

In Before, at least the Before that I remember, these tragedies were left, in the end, to the families and the friends. We watched our televisions and mourned. We talked about it at work. Then we moved on. The event: plane crash, bombing, accident, murder -- faded to little more than a headline in the year-end retrospective, played in slow-motion, set to mournful music. Did you ever feel, as I did, that sometimes you had to make yourself remember to feel sad, that you had to fill this obligation?

But now there are still nights when I wake up from the same dream. In it I see the skyline of New York in blinding morning sunshine. I see everything we saw hundreds of times. A plane diving, aiming; the towers falling, despite my pleading -- a plunge that lasts seconds or maybe hours. There is never any sound, until this voice that I suppose is my own asks, "Did this really happen?"

Then I jolt awake with the vision still fresh. Yes. It was real.

"We’ve lost our innocence," the media kept saying from the beginning. For the longest time, I couldn’t grasp what that meant. The act of stealing took just a matter of minutes, but understanding what has been stolen has been much slower in coming.

Yes, losing my innocence means climbing to the top of a very tall building and immediately looking down and imaging how it felt to fall and keep falling.

Or seeing a Middle Eastern man on the subway who avoids my gaze and fighting a nagging fear, then feeling guilty for feeling afraid. It’s when the mild butterflies that once came with flying in an airplane are replaced by a clammy-handed, gut-wrenching, grim expectancy..

Yes, loss of innocence is all of those things, but when they said we were forever changed I thought there would be this obvious shift. Foolishly I thought we’d all laugh more quietly or the sun would seem dimmer and this whole country would just, I don’t know, look different somehow.

Instead we go on doing everything beautiful and awful and mundane that we have ever done, and the memory lurks in the corners. I can be reading on a perfect summer day with a warm breeze -- laughing on amusement park rides -- buying groceries – sitting in traffic. Something reminds me. Something whispers in my ear and ever-so-slyly taints the moment.

September 11 has left me with a lingering sense that something important is missing. I’m pretty sure we will never get it back. And I miss it with this barely perceptible ache, like a sigh for no good reason, or a tossed sleep full of dreams just past my ability to remember.