Book Review: The ONE Thing — The Book I Found in Dental School That Changed How I Think About Everything

Dr. Mike Mackney, DDS  ·  Invest with a DDS

I was a third-year dental student when I found this book.

It was a shorter clinic day — rare — and instead of heading home to study, I wandered into a Barnes & Noble with no real plan. I ended up in the business section, flipping through spines, and one title stopped me cold.

The ONE Thing.

I bought it on the spot and finished it in two days. Not because I had extra time — I didn't — but because every page was saying out loud something I hadn't been able to put into words yet. I was in one of the most demanding academic environments of my life, trying to do everything well, constantly feeling like I was behind, always aware of a hundred things that needed to get done. And this book told me I was holding the problem completely wrong.

I've reread it three times since. It still delivers.

Why Healthcare Workers Need This Book More Than Anyone

Here's a pattern I've noticed in almost every healthcare worker I know, including myself for most of my career:

We want to be ten years ahead of where we are right now.

We want the paid-off debt, the established practice or senior position, the financial freedom, the schedule we actually control, the life that looks like what we pictured when we were grinding through boards. We want to already be there. And because we're not there yet, the gap between where we are and where we want to be feels like a problem to solve — which usually translates into doing more, taking on more, staying later, starting another thing.

The result is a specific kind of exhaustion that's hard to name. You're busy constantly but not sure you're moving. You have seventeen priorities and can't figure out which one is actually the most important. You're capable of a lot, so you try to do a lot, and you end up spread so thin that nothing gets your full effort.

Keller has a word for this. He calls it chasing two rabbits.

"If you chase two rabbits, you will not catch either one."

— Russian proverb, cited in The ONE Thing

You're not behind because you're not working hard enough. You're behind because you're trying to move in too many directions at once. Effort isn't the missing ingredient. Focus is.

The Domino Effect — Why Life Is Sequential, Not Simultaneous

This is the concept that hit me hardest when I first read the book, and the one I come back to most.

A single domino can knock over another domino that is 50% larger than itself. That's not a metaphor — it's physics, demonstrated in a 2001 experiment with plywood dominoes. Each one topples the next, and because each next one is bigger, the chain builds geometric momentum. Start with a 2-inch domino. The 10th in line is as tall as an NFL quarterback. The 18th is the height of the Leaning Tower of Pisa. The 23rd is the Eiffel Tower. The 31st clears Mount Everest. The 57th would nearly reach the moon.

All from a 2-inch domino doing its job.

The point isn't that life is a series of dominoes falling automatically. It's that success is sequential, not simultaneous. You don't achieve extraordinary results by doing ten things at once. You achieve them by identifying the right first domino, knocking it down, and letting it topple the next one in line — which is larger than you could have reached without it.

"Success is built sequentially. It's one thing at a time."

— Gary Keller, The ONE Thing

For a healthcare worker trying to build something outside the clinic, this reframes everything. You don't need to launch the course, grow the audience, master investing, pay off the loans, and start the business simultaneously. You need to identify your first domino — the one action that, if done consistently, makes the next one reachable. Then knock that one down. Only that one.

What does your first domino look like? Maybe it's publishing one piece of content a week. Maybe it's reading one financial book per month until you understand investing well enough to start. Maybe it's having one honest conversation with a financial advisor about where you actually stand. Small. Specific. And if you pick the right one, it starts a chain you can't currently see the end of.

The Focusing Question — The Most Useful Thing I've Taken from Any Book

The entire book is a setup for this one question. Keller calls it the Focusing Question, and it comes in two forms:

One question for the long view. One question for today. Ask both. Keep asking both.

What makes this question powerful isn't that it's profound — it's that it's specific in a way most goal-setting isn't. Most people operate on a vague sense of what they want. They want to be "financially independent" or "less stressed" or "more present." Those aren't targets. They're feelings. The Focusing Question forces you to collapse the abstract into the concrete: not "I want to build wealth," but "what is the ONE thing I can do today that moves me toward that?"

For healthcare workers, this question cuts through a specific kind of noise. You have clinical obligations, personal goals, financial pressure, and probably three half-started side projects. The Focusing Question isn't asking you to rank all of them. It's asking you to identify the one action — just one — that makes the most progress on what matters most. Everything else waits.

"Extraordinary results are directly determined by how narrow you can make your focus."

— Gary Keller, The ONE Thing

Goal Setting to the Now — Working Backwards from Where You Want to Be

Here's the framework that ties the dominos and the question together, and the one that actually changed how I plan.

Keller calls it "Goal Setting to the Now." The idea is simple but counterintuitive: start at the end and work backwards to today.

That last box — "right now" — is where most people start and stop. They think about what to do today without anchoring it to where they want to be in ten years. The result is a very busy life that isn't necessarily moving in the right direction.

Goal Setting to the Now forces the opposite. You start with the full picture and trace it back to a single action that you can do today. Your "ONE Thing right now" is nested inside your weekly goal, which is nested inside your monthly goal, which is nested inside your annual goal, which is nested inside your five-year goal, which is the foundation of the life you're actually trying to build.

It's one of the clearest frameworks I've ever seen for bridging the gap between ambition and daily action.

The Six Lies That Are Keeping You Stuck

Before Keller gets to the solutions, he tears apart six beliefs that most high-achievers hold as truth. These hit particularly close to home in healthcare culture.

That second lie — multitasking — is worth slowing down on for anyone in healthcare. The profession rewards the appearance of juggling. You manage five operatories, a full schedule, staff issues, insurance calls, and patient anxiety simultaneously. That's not multitasking — that's context-switching, and it works in a clinical environment because it's required. But when you bring that same mode of operating to your personal and financial life, it produces the same fragmented output: a lot of motion, not a lot of progress.

And the willpower lie. If you're scheduling the most important non-clinical work — the financial planning, the learning, the building — at the end of a long day in clinic, you're fighting biology. You've spent eight hours making precision decisions under pressure. Your willpower tank is close to empty. Keller's prescription is clear: protect your mornings. Do your ONE Thing before the world makes its demands on you.

"Success is actually a short race — a sprint fueled by discipline just long enough for habit to kick in and take over."

— Gary Keller, The ONE Thing

Time Blocking — How to Actually Make It Happen

Keller's most tactical concept: block time for your ONE Thing the same way you block time for patient appointments. It goes in the calendar. It has a start time and an end time. It is not negotiable.

He recommends four hours of uninterrupted, protected time daily for your most important work. That's not realistic for most healthcare workers on a full clinical schedule. But here's the principle that matters: if it's not in the calendar, it doesn't exist.

The key is sequencing. Clinical work is mandatory and it pays the bills — it doesn't go away. But if your personal growth, your investing education, your business building, or your financial planning only happens with leftover time, it will never happen consistently enough to move. Your most important non-clinical work needs a slot that comes before the day makes its demands on you.

How to Apply This Starting This Week

What I Actually Took From This Book

When I found this book in dental school, I was trying to be good at everything simultaneously. Great clinician, high board scores, healthy, social, financially responsible — all at once, every day, with no trade-offs. I thought that was what competence looked like.

The ONE Thing reframed that. Competence isn't spreading yourself across everything. It's knowing which thing matters most right now, and giving that thing the attention it actually deserves while letting the other things be temporarily underserved.

That's not laziness. That's strategy.

The version of me that picked this book up in Barnes & Noble didn't have a practice, a newsletter, an Airbnb, or a real estate portfolio. He just had a schedule that felt overwhelming and a vague sense that the life he wanted was somewhere in the distance. This book didn't give me a shortcut to that life. It gave me a way to identify the first domino — and the discipline to actually knock it down instead of standing in front of all of them and wondering which one to touch first.

Start smaller than you think you need to. Pick the right first domino. Stay on it until it falls. Then find the next one.

That's it. That's the whole book.

The ONE Thing by Gary Keller & Jay Papasan · Available everywhere books are sold · ~240 pages · ★★★★★

Dr. Mike Mackney, DDS  ·  Invest with a DDS  ·  investwithadds.com