Overnight, I found myself sitting in a very different perch: a hard metal chair, looking across a desk at a doctor whose expression was way too full of empathy for my liking. His eyes told me I would die soon. It was late spring. I had seen my last autumn in New York.

The verdict I received in the last week of May 2005 — that it was unlikely I’d make it to September — turned out to be a gift. Honestly. Because I was forced — at the age of 53 — to think seriously about my own death.

Which meant I was forced to think more deeply about my life than I’d ever done.

As CEO and chairman of KPMG, the $4 billion (£2.32 billion), 20,000-employee, century-plus-old partnership, one of America’s Big Four accounting firms, I was not a man given to hypotheticals — too straight ahead in my thinking for that — but just for a moment, suppose there had been no death sentence. Wouldn’t it be nice still to be planning, building and leading for years to come? Yes and no. Yes, because of course I’d like to have been around to see my daughter Gina graduate and marry and have children (in whatever order she ends up doing all that). To spend next Christmas Eve, the day before my older daughter Marianne’s birthday, eating and talking and laughing the way we did every year. To travel and play golf with my wife of 27 years, Corinne, the girl of my dreams, and to share with her the retirement in Arizona we’d planned for so long.

But I also say no. No, because, thanks to my situation, I’d attained a new level of awareness, one I didn’t possess in the first 53 years of my life. It’s impossible for me to imagine going back to that other way of thinking, when this new way has enriched me so. I lost something precious, but I also gained something precious.

In my past life, here was a Perfect Day: I’d have a couple of face-to-face client meetings, my favourite thing of all. I’d meet with at least one member of my inner team. I’d speak on the phone with partners. I’d complete lots of the items listed in my electronic calendar. And I’d move ahead in making our firm a great place to work, one that allowed our people to live more balanced lives.

For me personally — for any executive, but especially the top guy — that last plank in the platform was particularly difficult to achieve. Don’t get me wrong: I loved my firm. I was passionate about accounting. (Don’t laugh.) But the job of CEO, while of course incredibly privileged, was relentless. My diary was perpetually extended out over the next 18 months. I worked weekends and late into many nights. I missed virtually every school function for my younger daughter. My annual travel schedule averaged, conservatively, 150,000 miles. For the first ten years of my marriage, when I was climbing the ladder at KPMG, Corinne and I rarely went on vacation. Over the course of my last decade with the firm, I did manage to squeeze in workday lunches with my wife. Twice.

Before this starts to sound like complaining, I must be honest: As long as I could handle such a high-pressure position, I wanted it. As profound as my devotion to and love for my family were, I could not have settled for a job just because it guaranteed that I could make PTA meetings. People don’t walk into the top spot. They’re driven.

When Corinne and I showed up at the neurologist’s office on Tuesday, May 24, we were both convinced that the drooping of muscle in my cheek and at the corner of my mouth was caused by something stress-related, probably Bell’s palsy. I was asked some questions, then put through what seemed a pretty standard physical exam. The neurologist said that she wanted me to come in for an MRI first thing the following morning. This was one time where the virtue of promptness did not gratify me — getting bumped to the head of the MRI line was not the sort of privilege you want to experience.

A week later, the biopsy that was supposed to take two hours took three. Halfway through, the surgeon came out to tell Corinne that the first tissue sample he’d removed from my brain was “necrotic” — dead. Not dying, but already dead. Later, when the doctor could address Corinne and me together, he recommended radiation, which might provide a couple of extra months more than whatever I had left. There was no cure, he said. “This is terminal.”

My days as a man at the top of his game, vigorous and productive, were done, just like that. The whole of my life, I had expected people to operate at a high standard. If they didn’t, they might lose my confidence. I don’t mean to say that I lacked compassion; it’s just that, in the business world, our index for evaluating people was competency. It had to be. If someone said something that was carelessly conceived — whether it was one of the firm’s senior partners or my teenage daughter — I was not above telling him or her that it was “a stupid thing to say”.

My daily experience at the radiation clinic made me realise that was not the index I could use any more. Things don’t go according to plan. In fact, they almost never did. Sitting in that room, waiting for my turn to have the waffle-mask put over my face so they could zap my brain with laser beams, I watched people around me grow frustrated. I tried not to let it happen to me.