My time as a medical student has quickly come to an end. This past winter, with nearly four years of arduous study, countless examinations and numerous clinical rotations under my belt, I couldn’t help but think, Yes, I’m ready to be a doctor.

And then I became a patient.

I’d always thought I knew what it’s like to be the patient. For much of my childhood, my father suffered from chronic fatigue syndrome, a multifaceted, disabling illness whose cause is unclear.

On Sunday afternoons, my father’s health permitting, we would drive around the state to various support groups. Listening to the participants through medically untrained ears, I drew two conclusions: (1) These peoples’ lives had gone from “full speed ahead” to “brakes on” without warning; and (2) their disease had no cure.

They didn’t look sick, yet many, like my father, were too weak and fatigued to work. As a kid, I was in awe of the doctors who spent time helping these patients cope with pain and adjust to life with a chronic disease.

When I got to medical school, I spent hours listening to patients’ stories–not because I had to, but because I wanted to. Because if it were my family member with the breathing tube or the bedpan, I would want someone to sit with them when I couldn’t be there. I thought that if I sat and listened to their pain, I just might understand it. I might be able to fix it.

But the truth is that, no matter how empathetic a physician you believe you are, it’s hard to fully grasp the experience of being a patient until you become one.

I went to bed one night this past January feeling healthy, able-bodied and happy. I awoke a few hours later with inexplicable, electrifying leg pains that made my heart race with fear. In my gut, I knew something was terribly wrong.

The next four months felt like a nightmare set to AutoPlay on my iPod–each day was a different volume of awful. It felt as if explosives had been planted in my calves. My lower legs not only ached, they tingled and burned nonstop. Within moments of standing, they would feel so tight that I couldn’t take more than a few steps. I was bedbound for one month and functionally disabled for the next three. Tasks that required standing–showering, laundry, making an omelet–became nearly impossible. I needed taxis to get to the hospital, and once I got there, I needed elevators.

Feeling scared and vulnerable, I did what anyone with access to healthcare professionals would do: I reached out to the brilliant physicians with whom I worked. The “ding” that signaled a reply in my email inbox was music to my ears. Someone cared; someone might have the solution.

Doctors’ appointments led to blood tests, and lab results led to more tests.

As a medical student, I’d never blinked when ordering IV fluids or repeating a patient’s complete blood count–he was in the hospital, it was necessary! Now, as the patient, I looked wearily at the phlebotomist’s blue rubber tourniquet as it approached, my arms still aching from prior sticks. The MRI’s loud clacking noises, the missile-like stabs of local injections, the crushing headaches that followed a diagnostic spinal tap…”When will this nightmare end?” I whispered to myself. “When will my life go back to normal?”

I knew that, unlike many Americans, I was fortunate to have health insurance and a support system that covered the financial and emotional costs of being sick. But still I struggled, mentally and physically. I’d always gotten a thrill from solving puzzles and helping other people; now, because of my baffling illness, I was forced to grapple with chronic pain and uncertainty–forced to ask others for help.

Doctors’ waiting rooms became an ordeal. I used to think that patients hate doctors’ waiting rooms because they have other things to do–more pressing matters, such as feeding parking meters and chauffeuring soccer carpools. But as I sat in the faux-leather chairs, leafing through month-old Time magazines, I realized that for people in physical pain, whose caretakers sacrifice a whole day of work to transport them, the waiting room is absolute agony.

The appointment du jour was my outing of the day, and it required a lot of time and energy to make it there. Then, once I’d arrived, I’d start to wonder, Can my legs handle the extra steps for a bathroom trip? What about the insurance papers?

The physical drain of being ill made me feel sad–a sadness that sometimes hurt more than the pain itself. But the mind games were the worst: Why did this happen? What if I could rewind the tape? Why am I being punished?

I worried that everything I’d worked so hard for and loved would slip away: How can I be a great doctor if I can’t walk? How can I give to others in my personal life, now that I’ve become so needy?

Over dinner one Sunday, my father told me, “You can’t beat yourself up. Being sick does that enough for you.”

But I did anyway. Despite the many medical-school lectures I’d sat through on the biopsychosocial aspects of illness, only now did I realize just how tightly entwined the body and mind are.

I finally understood why chaplain visits in the hospital are so sought-after. When medicine fails to provide insight, faith seems more appealing–and, ironically, more logical.

In time, it became clear that the neuropathic and muscular pain in my lower legs was likely caused by a virus that I’d caught. I may never know for sure what happened, but since there’s no evidence of neurological, muscular or bone damage, and all of my blood tests have come back negative, my physicians believe that I will make a full recovery. After months of consultations, medications, anesthetic patches, steroid injections and physical therapy, my legs are gradually returning to normal. Walking has become easier, and each day I’m determined to do a bit more.

Looking ahead, I know that residency will bring a new set of challenges. Regardless of where my career takes me, though, I’ll never forget the lessons I’ve learned from being a patient. As painful as it has been, this experience has helped me to understand what being sick is all about, and also what it means to be healthy. Like my father, I will never forget the doctors who continued to check up on me and advocate for my care when I was too tired and frustrated to do so for myself.

As physicians, we must use our brains to diagnose and treat our patients. To do so requires a lifelong commitment to study and hard work. But in order for me to truly grasp medicine–to fully see, hear and feel the patient in front of me–I had to become one.

This lesson is not quantifiable or testable, and I certainly would not want to relive it–ever.

But I am grateful for it, in a really big way.

Madeline Sterling is an internal medicine resident. This piece was originally published in Pulse — voices from the heart of medicine, and is reprinted with permission.