Simple things to focus on without needing outside help with: sleep, diet, exercise, and a means to reflect.
More advanced / things that might require help: blood work, therapy, medication.
Sleep: Many chronic conditions are exacerbated by lack of sleep. There's been a general push for better quality sleep lately, but I still feel like we're not placing enough importance on sleep. Without good sleep, your diet and exercise won't be anywhere near as effective. Some easy wins: blackout shades, white noise machine, avoid blue light in the evening, and find a consistent bed / wake time.
Diet: Your mental and physical well being is a rolling average of the things you eat. Cheat days are fine; cheat weeks are not. A lot of chronic conditions come from inflammation, which can largely be improved by eating smaller meals with more colors in them (for most people). We’re only just discovering how important a healthy microbiome is for both physical and mental health. Eat more things that have or had roots. Eat less red meat. Find a good probiotic. HYDRATE. Most people don’t drink nearly enough water—so many issues disappear when you get enough water. Easy wins: use spices, avoid fried food, consider intermittent fasting (good for inflammation) if your doctor is okay with it.
Exercise: I hardly do it for physical reasons (though they are very positive), but instead for chemical reasons. Exercise is very important for your brain, and to flush toxins. I play soccer and lift weights, but you might find something else that you enjoy. Getting your body moving can make a very big difference with chronic conditions. Get the lungs and blood pumping. Easy wins: go for a walk after eating, do 10 pushups + squats + situps after a Zoom call or when you finish a task.
Reflect: Whether you do a 5-minute journal, transcendental meditation, 'Getting Thing Done', or whatever system is popular today... give yourself time to zero out your “stress box” the same way people zero out their email inbox. I personally enjoy using an infrared sauna several times a week—30-45min of uninterrupted time to let my thoughts go. An adrenal system that is constantly bombarded by stress causes so many of the chronic diseases that people suffer from (such as my own thyroid). The more you learn to de-stress, the better you become at detecting when you feel mentally or physically stressed. It takes time. Easy wins: schedule time to unwind on a consistent basis, learn some simple breathing techniques (here is a good one: https://www.youtube.com/watch?v=6FyE3VOWJI0 ), find a ritual you enjoy.
Bloodwork, therapy, medication: it helps to have a few thorough blood panels done so you can get a good idea about where your body needs some assistance. Chronic illness doesn’t always manifest itself the same way in everyone. If you can afford it, find a doctor who charges per unit of time and not per visit; they will be better able to properly listen to your problems and work towards fixing the cause of the problem rather than just the symptoms. Just as a chronic illness doesn’t mean you’re broken, medication also won’t fix you. It takes time to figure things out and adjust your lifestyle.
Chronic illness can be very stressful, and sometimes people might tell you there’s nothing wrong with you even though you have the deep sensation that something is. Consider seeing a therapist. Doesn’t necessarily need to be for psychological reasons. I personally visit a physical therapist 2-3 times a month as a way to better understand how my body is feeling and where I can make improvements over time. Being receptive to help is a big first step for many people.