Noorullah Shirzada / AFP / Getty Images A suicide bomber blew up this vehicle, killing a U.S. serviceman in a nearby convoy in Kabul on Dec. 27.

Upon the occasion of the new year, Afghanistan and the United States have yet to nail down a U.S. troop presence beyond 2014, and the American people have concluded that the 12-year-long war in Afghanistan is not only the nation’s longest but also its least popular.

The two data points are linked. Soldiers who think about such things—and most don’t—will acknowledge that long wars and democracies don’t mix.

When the war in Afghanistan began on Oct. 7, 2001, most Pentagon officials said privately that it would be over in a year or two; some estimated six months. Double that duration for Iraq, launched 18 months later on Mar. 19, 2003. The Taliban and Saddam Hussein were ousted shortly after U.S. troops arrived. What did we do following their ouster that has been worth the added cost in U.S. blood and treasure?

Many families of fallen troops feel their loved one died for something, but they’re not sure precisely what. Many don’t think it was to keep their families safe back home, where, statistically speaking, your chance of dying from malaria is greater than being killed in an Islamic terrorist attack. (If you want to believe that it was those very wars that kept attacks so low, welcome to the military-industrial superiority complex.)

In both Afghanistan and Iraq, we ended up with failed efforts to build better nations in far-off lands that we barely understood. So wired on the adrenaline rush of war we never acknowledged that we have flubbed the running our own nation as we deployed to tell others how to run theirs. If you can’t balance a budget, you can’t build a nation.

There is something perverse the way these wars were fought. They were launched by Ivy Leaguers and their foreign-policy acolytes but waged by kids from land-grant universities and Sunbelt high schools. Sure, that’s not completely accurate, but as they say with nuclear weapons, close enough.

Meanwhile, 300 million disengaged Americans shopped as nearly 7,000 troops dropped. Congress grumbled, but seeing as it didn’t have the constitutional guts to debate and declare war, it was merely a guilty bystander. The unfinished wars will likely cost U.S. taxpayers $3 trillion, once all costs are calculated.

This is no way for a great nation to act. There’s a reason the Constitution mandates that only the Congress can declare war. We’re either all in or all out. Anything short of that too often leaves us tasting the bitter bile of our own making, as many will do this New Year’s.

Even with 47,000 U.S. troops still in Afghanistan, you hear chatter about the possibility of dispatching U.S. troops to Syria, to central Africa, to Iran.

It took 30 years for the nation to launch a war as stupid as Vietnam. We could do worse than to ensure it takes at least that long before we do it again.

Think of it as a New Year’s irresolution.