So: Today marks 15 years since the invasion of Iraq.

It was knowably a bad decision at the time. It became a worse decision when we realized that Saddam Hussein didn’t really command an arsenal of WMDs after all. There was never going to be a good end after that — how do you “win” a war initiated on false premises? — and so far there hasn’t been.

I was a couple of weeks short of 30 when the invasion. I turn 45 this April. I’ve gone from relative youth to middle age in what feels like the blink of an eye.

Since that day, we’ve learned a lot more about what Americans will tolerate: Torture. Mass surveillance. And a persistent belief that we can get everything to go our way, evidence be damned, with the application of little more force. Every failure to destroy our enemies brings forth new calls to summon the will, to summon the mother of all bombs, to kill more, and then to kill more than that, an so forth.

MLK has a famous quote: “The arc of the universe is long, but it bends toward justice.”

I don’t know if I believe that. It’s pretty to think so.

What I think is true is this: The arc of the universe is long, and the fight for justice never-ending. So are the setbacks.

George W. Bush begat Barack Obama begat Donald Trump. The invasion ended Saddam, gave birth to a new generation of militants, and eventually gave way to ISIS. Everything we’ve done to make things better has proven temporary, illusory —or even made things worse.

It’s easy to despair in the face of that. But too much despair allows injustice to take root. So we keep fighting.

What else can we do?