A lot of it boils down to mindfulness.

When I realise my mind is wandering into anxiety territory where I make up scenarios that stress me out, take a few deep breats (box breathing is nice for this), focus on where I am right now and what I'm doing. What is actually true right now.

Take time for hygiene. I got long hair so I only wash it about once a week, using a specific soap, that smells and feels nice, condition it with a vinegar solution, rinse thoroughly.
I also brush it every day and tend to wax my beard when I go out and trim it regularly.

I'm still pretty shaggy but in a way that I enjoy personally.

Besides these, I have very active hobbies, that I stick to once or twice a week. I get to physically exhaust myself, interact with people outside my daily routine, work on my skills to get better. I picked up reading again in my late 20s after over a decade of losing that interest. It clears my head in the evening when reading in bed and I'd say that habit improved my sleep.