Michael McDonald Is 'Grateful' for Lessons Learned After Wife's Breast Cancer Diagnosis: 'She Put Us First' (Exclusive)

The Doobie Brothers frontman’s new memoir, ‘What a Fool Believes," is out on May 21

Michael McDonald is opening up about an emotional period in his life.

Speaking with PEOPLE ahead of the publication of his new memoir, What a Fool Believes, out May 21 from Dey Street Books, the Doobie Brothers legend, 72, is looking back on the “courage” of his wife, Grammy-nominated singer Amy Holland, after she received her breast cancer diagnosis — and what he learned along the way.

"I'm a firm believer in the worst things that happened to us inevitably without fail, turn out to be the best things that ever happened to us if we survive them," he says, of that challenging period. "When you look back on them, you realize that was the best thing that ever happened to us...It's kind of the way life works and maybe the way God intended it to work.

Holland, who married McDonald in 1983, received the diagnosis in 1995. The couple has two children together: Scarlett, 33, and Dylan, 36. The singer says the ordeal taught him and his family more about love and each other.

"I remember at the bleakest part of that whole thing, realizing that my wife and I were discovering what it means to love somebody else in ways that we might have never discovered it any other way," he shares. "And although I wouldn't want to go through it again for any reason, I am grateful for those lessons...We came to realize how much we did care for each other and how much we did admire each other."

“I was just trying to be there for her,” McDonald continues. “But I sure learned to admire her and her struggle and how she put us first, even at the darkest times in that struggle. That says a lot about her.”

Read more in an exclusive excerpt shared with PEOPLE, below.

In 1996, when we had been enjoying our new life in Nashville for a little more than a year, Amy was tending to a new garden she had planted. We hadn't gotten around to landscaping yet, so there was no sprinkler system in place, and she had to literally go down the hill to fetch a pail of water. One day, as she was carrying the buckets from the pond back up to the garden, she felt something in her breast — a knot that didn't seem to ease up. Knowing enough to be concerned, she went and got a mammogram, and that's when they saw it: a tumor.

At first, I managed to not go to the darkest place, imagining the worst outcome. I somehow decided there was no need to go there till I needed to go there; I determined there must be a way to solve this, and we'd find it.

Related: How Michael McDonald and Paul Reiser Teamed Up to Co-Write the Doobie Brother's New Memoir (Exclusive)

Still, there are moments when reality knocks at the door of hope with a message you don't want to hear.

I waited anxiously near the nurses' station outside of where Amy underwent surgery to remove the tumor to be biopsied. When I was informed that the surgery was over and Amy was in recovery, I approached the nurses' station to ask when the results might come through from the lab. I assumed it would fall to the surgeon to walk us through the results and the prognosis as soon as he was free, but the nurse on duty cut to the chase when she answered simply,

"Yeah — it's cancer."

It felt like a gut punch. I broke down right there in front of this woman I didn't even know. I don't think I realized just how stressed and tense I was. I apologized to the nurse. "I'm sorry. It's just ... you caught me by surprise."

I wanted so badly to hear that it was nothing, but that wasn't what I heard. However well I thought I had prepared myself for the worst, it obviously wasn't enough.

Based on just that tumor biopsy, the doctors weren't sure precisely how advanced the cancer was, but knowing it to be an aggressive form, they had removed 14 lymph nodes from under her arm for testing during the surgery, and it would be a week or so before we got those results.

We kept busy in the meantime, but it seemed like an eternity. I remember I was doing some grading in the corrals next to the house when I saw Amy burst out the front door, running toward me holding both hands over her mouth, visibly upset. I jumped down off the tractor and ran to her. She collapsed in my arms and in a trembling voice told me that the doctor's office called; out of the 14 lymph nodes they removed, 11 turned out to be positive.

Related: Stars Who Faced Breast Cancer and Shared Their Stories

That alone sounded so ominous. They still refrained from making any certain judgment about what stage it was or giving any prognosis over the phone, but suggested we meet with the oncologist at our earliest convenience. We wasted no time making that appointment, hoping it would shed more light on our situation.

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The kids were still quite young-Scarlett was 4; Dylan, 8 — so we didn't initially share the severity of the news with them, and we did our best to put on our bravest faces, but it wasn't easy.

Going to see Scarlett in her school's spring recital that first week after the diagnosis, I remember Amy looking at our daughter onstage, and I just knew she must've been wondering if she would even be here for this come next year.

That period of uncertainty was one of the most torturous points of this journey for both of us, but it was also in that moment, I believe, that Amy decided whatever she had to do to be there next year and stay in her kids' lives, she was gonna do it. One of Amy's greatest assets in all this would be her stubbornness. We learned that when positive thinking wanes and gives way to fear or despair, plain old stubbornness comes in pretty handy. There were also the angels who came along at the right time to help us on this sojourn.

It was still the early stages of stem cell rescue treatment, and wanting to make sure we were getting the best medical advice, we flew up to New York to get a second opinion from a highly regarded expert, a Dr. Holland - which all by itself felt encouraging; when the doctor has the same last name as the patient, that's got to be a good omen (even if it was just Amy's stage name).

Dr. Holland, it turns out, was actually one of the pioneers in early chemotherapy research, so his word carried a lot of weight with us. When he told us that he personally knew of Dr. Greco, the oncologist we were seeing in Nashville, and assured us we couldn't be in better hands, we were greatly relieved.

There would be many touch-and-go points throughout this or-deal, not to mention a whole litany of residual side effects from the treatment that no one told us about. And because it was still in a clinical trial phase, there were consequences they may not have even known about yet. For instance, Amy would go through sudden and severe menopause, resulting in a chronic loss of bone density and bouts of lymphedema - enough to cause even the most determined person to despair. At times it seemed too much, but I've never known anyone more courageous than my wife as I've watched her get over each and every hurdle in her path to be here for the ones she loves.

During one of those intensely potent chemo sessions toward the end of the oncology regimen (which by this point was already making her pretty weak and sick), I remember sitting silently with Amy in a room full of other patients in other beds, all receiving chemo-therapy. There was a moment when she looked at me with a sad, resigned smile as if to say, "I'm sorry to put you through this." Right then, in the middle of all she was enduring, while fighting for her life, she was mostly concerned about me. 

It was in that moment I realized that the real character of love can only be seen in moments like these, the desperate, scary, and uncertain times. When the measure of who you really are, your true character, is revealed in how much you care about someone else. At that moment, with just a scarf around her bald head, no eyebrows, no eyelashes even — just her blue eyes looking out at me from behind an ashen complexion - she was never more beautiful.

From What a Fool Believes by Michael McDonald with Paul Reiser. Copyright © 2024 by Michael McDonald. Reprinted courtesy of Dey Street Books, an imprint of HarperCollins Publishers.

What a Fool Believes will hit stores on May 21 and is now available for preorder, wherever books are sold.

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