Several years ago, a physical therapist told me to never fully give in to the pain. To never just spend the day in bed.

“Not possible,” I said. “I have a five-year-old son. Staying in bed all day simply isn’t an option.”

I live with an invisible disability, a rare autoimmune disease called Undifferentiated Connective Tissue Disease (UCTD). My rheumatologist described it to me as having overlapping symptoms of lupus, rheumatoid arthritis, and myositis—without it being any of those distinct diseases. On a daily basis I experience fatigue, weakness, and pain in my legs, with my left leg consistently worse than my right.

I first became sick in 2010, when my son, Ryan, was just two years old. At the time, I didn’t realize my symptoms were the beginning of a chronic illness. I thought I had an illness that would be treated, fixed, and ultimately healed.

However, that’s not how autoimmune diseases work. Many are outwardly invisible. Most are permanent. All are life-changing.

I never could entertain the idea of a day in bed. My husband works in retail, meaning his hours often fluctuate from week to week. He may be home for dinner some nights, but not all nights. Plus, I’m a very hands-on mom. I don’t want to stay behind resting while my husband and son go to the park. These moments, when our son wants us to be with him, are fleeting. I want to grab onto them with all my might for as long as I can.

I never thought of the possibility of “giving in” to my disease, my despair, and my sadness.

All because of Ryan.

Ryan is my biggest inspiration. He is the reason I push myself to do the things I do. Games of handball. Kicking a soccer ball back and forth. Neighborhood bike rides. Horseback riding. Hours spent exploring the Natural History Museum and the Science Center.

I push myself to do as much as I can, in hopes of filling up Ryan’s memory bank. Because who knows what the future holds? And while every parent has that vague fear—the fear of What if I can’t take care of my child? What if I’m not around to watch my child grow up?— living with a chronic illness has taken that vague fear and made it more real. And now those fears have grown and expanded and also include What if my legs worsen? and What if I become dependent on a cane, walker, wheelchair, or some combination?

Ryan doesn’t remember me “before.” He doesn’t remember when I used to leave our house to teach “the big kids.” In reality, I was an elementary school teacher, but when you’re three years old, nine- and ten-year-olds are definitely “big kids.” Ryan doesn’t remember when we used to walk to our neighborhood bookstore instead of driving.

It saddens me that Ryan doesn’t remember our hour-long neighborhood walks. How I used to put him in his stroller and talk to him about the cloud that looked like a turtle, point out a hummingbird momentarily pausing on a bird of paradise, or watch a squirrel scamper up a tree.

In all fairness, he most likely wouldn’t remember those days because he was so young at the time. But it saddens me that Ryan doesn’t remember how I used to be. Healthy. He doesn’t remember when bottles of prescription medication weren’t always on the kitchen counter. He only knows me as I am now—a woman living with legs that hurt.

It breaks my heart that Ryan has learned a powerful lesson at such a young age. People get sick. All different kinds of sick. Through no fault of their own. And sometimes there’s nothing you can do to make the illness go away. The only thing you can do is learn to live with it as best you can.

But there is a flip side to all this.

There has to be.

It is my hope that living with this invisible disability, raising Ryan while navigating this unpredictable illness, is perhaps the greatest way I can teach him essential life skills of perseverance and resilience.

Ryan has not seen me give up. He has not seen me become a patient first. I do not allow my illness to define me. I’m still up and about each day, trying to live my life as fully as possible. Pursing my passions—writing, reading, and gardening. And pursuing my chores and responsibilities—grocery shopping, writing bills, and cleaning out closets.

It is my hope that Ryan is also learning that you don’t know someone’s whole story by looking at them. You can’t possibly know someone’s pain, scars, injuries, and illnesses from a quick glance. There is so much more than what is visible on the surface.

I retired from teaching after 12 years on the job. I became a stay-at-home mom, an unexpected change in my career that I never anticipated. And again, it’s a powerful lesson Ryan has learned early on. You can’t plan for everything. Jobs change. Life paths change. And sometimes you can’t do anything about it. You can’t control the change; you only control how you react to those changes. I hope I’ve taught and continue to teach Ryan that you don’t give up. You try your best at everything regardless of what “everything” looks like.

Several months ago, a classmate in a creative writing class I enrolled in gave me some encouraging words. After workshopping one of my personal essays earlier in the day, she told me something I wasn’t expecting to hear.

“Ryan’s lucky,” she told me.

I looked at her, not quite sure what to say in response.

“Ryan’s lucky that he’s growing up with you as his mother. You’re teaching him so much. He’ll grow up to be such a patient, understanding, empathetic young man.”

I hope so.

Wendy Kennar is a freelance writer and former teacher. Her writing has appeared in a number of publications and anthologies, both in print and online. You can read more from Wendy at www.wendykennar.com where she blogs about books, boys, and bodies (specifically living with an invisible disability).