Leaning my car seat back so I can rest a bit while I wait for my daughter to get out of school, I become more aware of how excruciating the headache is. Exhaustion from single parenting is a familiar reality, but recovering from traumatic brain injury is a whole new world of tired.

Several people have said to me, “you seem fine.” And it’s true that on the surface — except for the tinted eyeglasses — it looks like I’m functioning at a normal level. But the symptoms caused by the concussion I sustained at the end of June permeate every aspect of my life; everything is much more difficult. If I do too much in a day, for example, the thought organization required to plan and prepare dinner for my children is too much. I’m not talking about the end of the day exhaustion any parent may feel — I’ve certainly felt too tired to cook some days, unrelated to the concussion. I’m talking about not being able to think well enough to get the tasks done.

Because I “seem fine,” I started thinking about all of the people walking around today who are living with what some people call “invisible disabilities.” According to the Robert Wood Johnson Foundation, approximately 110 million Americans are living with chronic conditions that may cause them pain, discomfort or other difficulties that cause serious challenges in their lives, and 27 million of those people are living with chronic illnesses that limit their daily activities.

It has been my experience that it doesn’t take much pain or discomfort to make day-to-day living much more challenging. There’s a snowball effect. When daily living is more difficult, stress builds up, which can affect sleep, which can lead to more difficulties. That’s just one of the frustrating cycles for those of us living with chronic conditions.

Talking with a friend about my experience seeming to be OK, but having difficulty with the simplest of tasks, I mentioned I might write about “invisible illnesses.” A woman overheard me and waved her hand at us. “I’ve got lupus!” she said. Lupus is just one of the many chronic illnesses that can at times be debilitating when it flares, but the symptoms can decrease and even go away for periods of time. When the symptoms are mild, a person with lupus may walk around feeling deeply fatigued, with her whole body aching, but she may still be able to perform tasks as needed at her job. She may seem fine, but she may not feel fine at all.

When I began my intake appointment a neuro-rehab center a few weeks ago, my eyes filled with tears several times. Being in a place where I didn’t have to explain that, yes, I seem fine but really I’m not, was a relief. They dimmed the lights in their offices, because they know concussion recovery frequently involves “photophobia,” discomfort because of light exposure. The administrative intake worker offered to help me with my paperwork, which I declined at first because, of course, I can fill out some simple forms, right? But, no, things that should be very easy end up wiping me out. I’m still not used to how little I can manage these days.

The odds are good that I will recover completely. It was clear to me that the occupational therapy, physical therapy and speech therapy professionals working with me know what they are doing. They work as a team, including communications with my neuro optometrist, who prescribed the special glasses I will wear for a few months. Our health care system is a mess most of the time, but I’m grateful to have found a place where I feel I’m in good hands. The coordination of care makes all the difference.

While I am in the midst of this difficult recovery, I’m more aware of how important it is that we not assume everyone who seems fine actually is fine. I keep coming back to a quote I’ve seen on the internet, that feels like important and useful advice. Words to live by: “Be kind. You never know what someone else is going through.”

Heather Denkmire is a writer and artist who lives in Portland with her two young daughters. Her small business helps nonprofit organizations win grants. She can be reached at column@grantwinners.net. Her columns appear monthly.