IT'S NOW NINE O'CLOCK in the evening. The toilet is up; the pee pails are distributed. Down at the edge of the river, where the dories and the rafts are securely tied to each other, the crew enacts an abridged version of the bedtime ritual on The Waltons—

"G'nite, Monte ..."

"G'nite, Kevin ..."

I unfurl my air mattress and crawl into my sleeping bag, and you're probably wondering: So what goes through the mind of a 43-year-old man who's about to spend the night sleeping on top of six poo cans?

Well, I should probably be planning how to rearrange those groovers in the morning, so that the Jackass will be balanced evenly for the enormous rapids downriver. But instead I'm dwelling on how badly I screwed up my run. Not just this afternoon's bungled trip through Horn Creek, mind you, but the longer, more misguided run down the river that is my life.

During my trial-by-fire odyssey as a poo-man, I've often wrestled with the question of why I chose to do this and whether it has been an enormous mistake. Whenever I take stock of all the regrets and missed opportunities I haul around like the rocket boxes on my raft—the career I've squandered, the women I've let down—I can't help but conclude that I've conducted myself like a jackass. By any accurate definition, my current state of affairs looks and sounds like failure. But on a night like this, as I lie on my boat floating in an eddy at the bottom of the canyon, with Jupiter's lantern swinging in the sky, it doesn't quite feel like failure.

Granted, I have spent some truly miserable moments on the river. But those ordeals have also been leavened by moments of simple, unvarnished perfection. I have seen summer thunderstorms send dozens of waterfalls simultaneously plummeting from the rimrock to the river. I've rowed past bighorn rams battling each other on the cliffs, the sound of their head-knocks echoing off the stone. I've napped on beds of columbine and hellebore orchids, and gazed at the turquoise waters bubbling from the subterranean pool that the Hopi believe to be the wellspring of life.

Those are wondrous things, to be sure. But the real reason I don't feel like a complete loser has less to do with the gifts that I've been given and more to do with what's been taken away. By stripping most of my pride, my apprenticeship has laid bare one of the more intriguing paradoxes of the Grand Canyon: the fact that this place has the power to render a person not only profoundly diminished but also radically expanded, often in the same breath. Of the many things that the canyon and the river supposedly offer, this may be the purest of them all.

So, yes, it's true: If I keep at this baggage-boat gig for a few more years, I may someday enjoy the privilege of rowing actual passengers down the Grand Canyon. In the meantime, the Jackass needs a captain—a role that commands, in my experience, an unexpected dimension of dignity and even a measure of grace. It's a job whose principal dividend, I suppose, is a subdued and somewhat battered frame of mind that, as the moon prepares to rise over the rim and the night cups the river in its hands, feels almost like happiness.