Things I've done (which seem to be helping)

Food:

I eliminated seed oils

I reduced carbs/sugar

I eliminated food additives (eg sodium nitrates)

I added more red meat

I drink ultra-pure water (which has fluoride removed along with everything else)

Habits:

I take cold showers (especially in summer)

I take off my shirt and sit on my balcony for 20-30 minutes around noon for sun exposure

I read 1-2 chapters of something educational during my sun exposure

Sleep:

I bought red LED night lights

I set all my screens to "night mode" which reduces blue light

(so I actually get sleepy shortly after the sun goes down)

When I wake up I look at the blue of the sky for a few minutes to help signal to my brain that it's time to be awake

I've tried some vitamin supplements but didn't see much benefit (and arguably had some downsides)

Now I eat carnivore-ish and haven't supplemented at all in something like a year and a half