I have just come off a phone call with an herbalist. For some people, that might be an unremarkable statement. They have many conversations with nutritionists, acupuncturists, cranial osteopaths, homeopaths. But not me. For most of my life, all 65 years of it, I have lived quite satisfactorily with the occasional attention of my G.P. and a quite unwarranted conviction that I am basically O.K.

“Basically O.K.” seems a good place to start when considering one’s health or wellness. Wellness, though, is a notion I have certain issues with. I’m not wild about having reached the age when instead of being greeted by “You’re looking great,” it is far more likely to be “You’re looking well.” Nobody says “You’re looking well!” to a young person.

But not only am I no longer young, in the past couple of years I have also become a member of the non-exclusive club of those who have had cancer, specifically of the breast. That experience kind of switched things up. When I got the diagnosis, after investigating an occasional, stabbing pain in my left breast, caused by a tumor that had cannily nestled under the breastbone, thus not showing up on the mammogram, my vision of myself changed.

Instantly, I was no longer assumed to have the constitution of the proverbial ox who would “outlive all of us,” as my friends used to say. I was suddenly bang up against the question of mortality, or so it felt in the panicky terror that took hold in those first few weeks. The future had always stretched out some ways ahead, even if the route was misty and unspecific. Suddenly, it had taken a sharp curve into territory that I couldn’t see or navigate.

When I visited one of the U.K.’s leading oncologists for a second opinion on my treatment, my most important question was “Is it O.K. to drink alcohol?” The idea that I was going to have to deal with cancer without the benefits of several glasses of wine or a cheering vodka gimlet was almost as terrifying as the illness itself. He assured me a glass or two was fine, but “probably not a bottle.” O.K., I thought. We’re on.

That was 18 months ago. When many people are diagnosed with a serious illness, they revamp their approach to well-being. But I have a missing gene in this respect. Although I was terrified to learn I had cancer, my continuing modus vivendi has been to live as if nothing all that serious has happened.

Naturally, there have been countless suggestions of practitioners I could visit who would supposedly boost my immune system and improve the state of my rickety body, but I have chosen to keep things consistent and enjoy myself as much as possible. The more I can marry that with not actively doing serious bodily harm, the better.

But have I managed to do the sensible thing and stop smoking my four cigarettes each evening? I have not. When it comes to knuckling down to intense health improvement, I am on the identical page to singer and songwriter Gillian Welch’s “Miss Ohio”: “I wanna do right, but not right now.”

The idea that I was going to have to deal with cancer without the benefits of several glasses of wine or a cheering vodka gimlet was almost as terrifying as the illness itself.

So back to the herbalist. Since part of my treatment involves a medication that strips my body of any vestige of estrogen that it might have left at this age, I now attribute any failings in my body to that deficit. Every creak, every weight gain, any sleeplessness—I never blamed any of this on menopause for reasons that remain unclear, but now this damn medication is responsible. So it’s not my lifestyle I am asking the herbalist to address, but the pesky pill. Yes, I see the inconsistency.

It is as though time—the passing of the years, rather than cancer—has made me examine the bargains that we make in life. If I am going to continue to enjoy half a bottle of an Italian white, those cigarettes, red meat, and croissants, I accept there has to be some deal done with mortality, or at least with my body, which is admirably stoic in the face of a certain amount of pleasurable toll.

I now take several supplements each morning. I am attempting to weight-train, and have become somewhat obsessed with a weighted Hula-Hoop, which I whirl around my waist listening to A.O.R. from the 70s. “More than a Feeling” is excellent company. I have stuck to a weekly yoga class for many years, and I soldier on with my twice-weekly runs. I have just finished Trollope’s The Way We Live Now as soundtrack, so you may have some idea of my speed.

Some of my great friends get a sense of achievement from putting their bodies through all kinds of exercise and deprivation. They probably make the entirely sensible equation that a healthy lifestyle makes them a healthier person.

Deep down, though, I fail to make this correlation. I take the view that we simply don’t know what’s going to get us. Joan Didion says it better in The White Album: “I had at this time, a sharp apprehension not of what it was like to be old, but of what it was like to open the door to the stranger and find that the stranger did indeed have the knife.”

Given the likelihood of that scenario happening at some time or other, I take the view that indulgence trumps deprivation. But who knows whether I’ll feel that the odds were worth it when I’m confronting that stranger, and realize that I failed the trial run.

Alexandra Shulman, the longest-serving editor of British Vogue, is a columnist for The Mail on Sunday and the author of the memoir Clothes … and Other Things That Matter