She was a regular customer, the kind you came to recognize even when she wasn’t coming to the pharmacy. She liked to shop. Candy, cosmetics, stationery, whatever else caught her attention as she wandered the aisles of the chain drugstore.

Once or twice a month, though, she came to see me. She had Type 2 diabetes, and I filled her prescriptions for insulin and the syringes and testing supplies she needed to manage it. She was probably in her late fifties or early sixties. I wasn’t yet thirty.

One day, as she stood at the pharmacy counter, I happened to glance into her shopping cart. There were miniature candy bars, candied orange slices, gumdrops, cookies—the very things I knew she ought to be limiting. I hesitated before saying anything. She wasn’t an especially warm woman, and our conversations could have an edge. Still, I was her pharmacist. I knew diabetes wasn’t managed by insulin alone. Diet mattered. So I gingerly suggested that she might want to be careful about how much candy she was eating.

She snapped back. “Well, I’m taking my insulin, so I’m okay, and you should know that!”

I did know something. I knew the insulin didn’t make the candy harmless. I knew what diabetes could do when it wasn’t well controlled. And standing behind that pharmacy counter, young and confident in what I had been taught, I knew what she should be doing.

What I didn’t know nearly as much about was people.

We had a word for patients like her: noncompliant.

Healthcare professionals used it freely. A patient didn’t take a medication as prescribed, follow the recommended diet, check a blood sugar, stop smoking, lose weight, or return for follow-up care. We explained what needed to be done. The patient didn’t do it. Noncompliant.

Health care providers didn’t intend for the term to be cruel. Most of us genuinely wanted our patients to get better. We had been trained to recognize disease, understand treatment, and explain what could happen when patients didn’t follow recommendations. When someone repeatedly ignored advice that seemed so obviously beneficial, frustration could creep in. Why wouldn’t they do what they knew they should do?

It took me years to recognize the weakness in that question. Knowing and doing are not the same thing.

We know exercise is good for us, yet the comfortable chair wins. We know saving for the future matters, yet tomorrow always seems far enough away to begin later. We know certain foods aren’t good for us, yet we eat them anyway. We know relationships require attention, apologies sometimes need to be made, and careers rarely move forward simply because we wait for someone to notice us.

Knowing isn’t usually the hard part. Doing is.

And perhaps that woman standing at my pharmacy counter understood more than I gave her credit for. She almost certainly knew that candy wasn’t good for her diabetes. Another lecture about sugar probably wasn’t going to provide some missing piece of information. The more interesting question—the one I wasn’t experienced enough to ask then—was why knowing wasn’t enough.

Shakespeare understood the problem long before we had words like compliance or behavior change. In Hamlet, Laertes is preparing to leave Denmark when he offers his sister, Ophelia, some earnest advice about how she should conduct herself. Ophelia listens, but she isn’t about to let her brother escape without a warning of her own. Don’t be one of those people, she tells him, who point out the “steep and thorny way to heaven” while choosing the easier “primrose path” for themselves.

More than four hundred years later, we are still walking both paths. We are remarkably good at knowing what should be done. We may even be better at recognizing what someone else should do. Spend less. Exercise more. Put down the phone. Eat better. Make the appointment. Have the difficult conversation. Stop putting off whatever we have been promising ourselves we will begin tomorrow.

The advice is usually sound. Following it is another matter.

Perhaps that is because knowing asks relatively little of us. Doing may ask us to surrender something—a pleasure, a habit, some money we would rather spend today, an evening on the couch, a comfortable routine, even the satisfaction of believing that we were right.

Sometimes the obstacle is greater than reluctance. A person living paycheck to paycheck may understand perfectly well the importance of saving and still have nothing left to save. Someone may know that exercise would be beneficial but be limited by illness, disability, time constraints, or other circumstances. Knowing what someone should do is easy when we aren’t living that person’s life.

That is something I understood imperfectly when I stood behind that pharmacy counter. My patient had diabetes. The candy wasn’t helping her. I was right about that.

But being right was never the whole story.

So what helps move us from knowing to doing? Part of the answer lies not only in the advice itself, but in how it is offered.

We’ve all encountered people who know a great deal and make certain that we know they know it. They instruct. They correct. They sometimes leave us feeling smaller than we did before the conversation began. Even excellent advice can become difficult to hear when it arrives wrapped in superiority.

And then there are the people who possess just as much expertise—perhaps more—but wear it differently. They explain. They listen. They tell us not only what they recommend but why. They invite questions. They don’t surrender their expertise, nor do they pretend that every choice is equally wise. But somehow, when the conversation is over, the decision feels as though it belongs to us.

I recently spent time with an adviser like that. He offered several recommendations, each accompanied by a thoughtful explanation. There was confidence in what he knew without a trace of arrogance about knowing it. I never felt instructed or diminished. I felt like a partner.

And I listened.

That experience made me think again about the woman with diabetes and her shopping cart. I’m curious how often, as healthcare professionals, we believed our responsibility ended when we had given patients the correct information. We explained the medication. We warned about the interaction. We recommended the diet, the exercise, or the follow-up appointment. If the patient didn’t act on our advice, we had a word ready: noncompliant.

But communication asks something more of us. People are more likely to consider difficult advice when they feel respected enough to examine it. They are more likely to take ownership of a decision when they have been invited to participate in it. Expertise matters enormously, but expertise and humility are not opposites.

The best advisers I have known don’t use their knowledge to make themselves bigger. They use it to reduce the distance between us.

That may be where doing sometimes begins.

Of course, it is easier to see the distance between knowing and doing when we are looking at someone else. I could see it in that woman’s shopping cart. Healthcare professionals could see it in patients who continued smoking, skipped medications, or ignored recommendations. Financial advisers see it in people who postpone saving. We see it in friends who remain in situations they complain about but never change.

The view becomes less comfortable when we turn the mirror around.

I have known that exercise is good for me, yet I have found reasons not to exercise. I have known that a difficult conversation needed to happen, but I have postponed it. I have received advice that I initially resisted, only to discover later that the person offering it had seen something I was not ready to see.

I have known better and not done better. Most of us have.

Perhaps that is why I am less comfortable today with the word noncompliant than I once was. It places the problem conveniently on the other side of the counter: I told you what to do. You didn’t do it. But human behavior is rarely that tidy.

Being willing to listen doesn’t mean doing everything someone tells us. Good advice can be wrong. Experts can disagree. Circumstances matter. We still have to question, weigh, decide, and sometimes say no. Being teachable is something different. It is the willingness to remain curious when advice makes us uncomfortable, to ask whether our resistance comes from thoughtful disagreement or simply from not wanting to change, and to consider the possibility that another person may see something we cannot yet see for ourselves.

I wish I could say I have always done that. I haven’t. But growing older has made me less interested in proving that I already know and more interested in discovering what I still have to learn.

I haven’t thought about that woman in years, but I can still picture her standing at the pharmacy counter, her shopping cart nearby. I don’t know what happened after she left the store that day. I don’t know whether she ever changed what she ate or whether another physician, pharmacist, nurse, or family member eventually managed to reach her. Perhaps no one did.

I do know that I was right about the insulin. Taking it did not make the candy harmless. Her diabetes required more from her than filling a prescription, and nothing I have learned since has changed that.

But something else has changed.

The young pharmacist behind that counter believed that knowing what was right and explaining it clearly should have been enough. If the patient understood but still didn’t act, the failure seemed to be the patient’s.

I no longer believe it is that simple.

Knowledge matters. Expertise matters. Good advice matters. But between knowing and doing lies all the complicated territory of being human—habit and fear, pleasure and circumstance, resistance and readiness, trust and choice.

Sometimes we cross that distance because someone helps us see what we could not see ourselves. Sometimes we cross it because someone offers knowledge without making us feel small. And sometimes, despite everything we know, we remain exactly where we are.

“Well, I’m taking my insulin, so I’m okay, and you should know that!”

She was wrong about the insulin.

But after all these years, there was something I should have known.

Knowing what someone needs to do is one thing.

Understanding what might help them do it is another.