“I am approaching my fiftieth birthday, Mr. Trout,” I said. “I am cleansing and renewing myself for the very different sorts of years to come.”

Later this month, I will submit to my first routine colonoscopy. (“It’s time,” the doctor had informed me, gently.) Some hours prior to that, I will drink a tall glass of what we shyly call prep solution, formulated to drive the gut into a self-cleaning paroxysm so that the surveyors might, flashlights in hand, enjoy an unobstructed view of the property.

Bringing the heavy bottle home from my local CVS, it occurred to me that this voluntary action will mark, objectively and inarguably, the end of youth. More than my retirement from software engineering over the past few years; more than my primary-care doctor saying “You’re not a kid anymore” last year; more than my fiftieth birthday, still more than a year away. It feels right to choose a moment completely under my own control, and not a gradual shift, external pronouncement, or arbitrary calendar date.

So I will drink, bear the brief unpleasantness that must accompany any professional poisoning, and then sleep, feeling nothing at all while specialists practice their unpretty but necessary art on my lifeless body. And then, if Providence allows, I’ll awaken into the next part of my life—what Kurt Vonnegut called “the very different sorts of years to come” in Breakfast of Champions.

I am ready to cross this threshold. My life, in so many ways, has never been richer. I don’t assume that my peak of personal or professional quality lies behind me, even if the longer part of my lifespan might. Barely a year into my second career as a technical writer within a huge organization, I still have so much to learn, and I know that I can, and I want to do it.

I feel exceedingly well provisioned for the road ahead, even as I know that the pavement will start cracking, and the incline begin to steepen, as the milestones pass. Preparing to meet the challenges to come, I continue to exercise briefly but intensely every day, and maintain my modestly careful diet. And it still works: another doctor last month pronounced my arteries clean and my heart eager to give me as much as I ask of it, for the present.

I will continue to accept the gift, for as long as I find it offered to me.