What Mr. Haass left behind was a country distinctly unsure of itself. Investment in Northern Ireland has soared in recent years. A sense of color and charm has seeped into the streets. Checkpoints have disappeared. Festivals abound. Sixteen years of peace have meant that a whole generation has grown up without the daily litany of violence.

At the same time, many Catholics and Protestants live in walled-off mini-citadels and their children go to separate schools. A rash of xenophobic attacks against Eastern Europeans have occurred in Belfast, with “Locals Only” scrawled on wooden panels placed over shattered windows.

And small eruptions of violence hit regularly; virtually every year the failure to agree on parade marching routes and the politics of flags serves up yet another reason for the Molotov cocktails to fly. It’s a small sky over Northern Ireland, but there’s a lot of smoke.

The people of Ireland and Britain still desperately want the peace to continue. It’s one of the few things that we have excelled at in recent years. It is a moral commodity. We have put a lot of energy into it. It makes us look good.

If it falters, it will be a disaster not only for us but for the rest of the world. Peace is not a local thing. That’s what makes it superior to war. War stays where war is. Peace belongs elsewhere, as well as at home. That’s part of its muscle. The presence of peace in Ireland is a lifeline, however tentative, to Syria, to Ukraine, to Colombia.

But the sense of exhaustion in Northern Ireland is a self-perpetuating time bomb. This is not just petty political squabbling. Peace — especially at the delicate age of 16 — can have an ego. It can turn off its calculating mind and fall into the dark pit of being satisfied with itself. Forging a continuing peace process means understanding that there are always going to be several viable truths. The peacemaker — as Senator George J. Mitchell, who negotiated the peace, learned in 1998 — must show the tenacity of a fanatic.

It is, of course, naïve to expect total reconciliation. Some grievances are so deep that the people who suffered them will never be satisfied. But the point is not satisfaction — the point is that the present is superior to the past, and it has to be cultivated as such.