They ran the 118th Boston Marathon yesterday on a perfect sunny day. Trees, late this year, were just bursting into flower; the weather was warmer than the runners ideally hoped for but it wasn't actually hot, and for the spectators it was perfect. I was watching with my nephew Dan's wife, kids, in-laws, cousins, and a million other spectators, twice the normal number. Last year a few weeks after the bombings Dan wondered if he should train to run the 2014 marathon. The "god damn it" was unspoken but loud. In the same tone I said if he did, I'd come cheer. So did thousands of more runners than usual and hundreds of thousands of spectators. The Boston Athletic Association offered the chance to run the marathon to anyone injured in the bombings; a number of them did, and one of those, who'd considered leaving town for the weekend, said this for all of us: "It seemed cool to run toward the city instead of away."

It was glorious, but it wasn't the same as it used to be. The air had an edge it never had before and everyone breathed a sigh of relief when the day was safely over. People commented sadly on that, thrilled to have taken the race back but feeling something had been irretrievably lost. I thought about that on the train back last night -- a train packed with sleeping runners -- and as a New Yorker I want to say this to Boston: that won't always be true. After Sept. 11 we felt that way about stunning autumn days. That's when NY is at its best but so many of us felt our autumn had been destroyed forever. But the glory and the darkness of humans is our ability to forget. As individuals, it's harder. People who were there will always live with it. What will happen in Boston as a city, though, is what happened here: as the disaster recedes in time, new people will weave themselves into the fabric of the city, people without those memories. People just arriving from other places, and people who are younger, growing up. The horror will get diluted both by time and by the number of people sharing your communal life. You'll get your race back, as we got our autumn.

This, of course, is both the good news and the bad news. We're sliding down the slope toward environmental catastrophe because of our talent for rising to a crisis and then moving on once the crisis is over. It's in our DNA, a reasonable response to the world where we evolved, when almost all crises were short-term. The tiger stalked you, you ran away, then you went back to your everyday life. No point in using your energy making plans to avoid being stalked by tigers, except maybe changing your path to the waterhole to skirt the tiger's lair. Now, however, we're being stalked by a huge and long-term tiger; and even if we manage to vanquish it in the coming decades -- a big if -- we'll have to permanently change our behavior and our understanding of our position on the earth in order to avoid it coming back for us again. Can we do it? I don't know. For now, I'm hopeful that the individual and communal determination, courage, and compassion I saw in Boston yesterday means that we can.