Food (including hydration), Sleep, Exercise
Manage all three carefully, but remember that 80% of perfection is enough
Modern life tempts us to be careless with all three, so a general principle:
* If you find yourself in a hole: first, stop digging
* It's not easy to change bad habits, but food is where modern life is most inclined to trick us. If you're not sure where to start, cut out "white foods".
PS: I looked for a good, simple definition of "white foods", but couldn't find one.
This is better than nothing, but I can't vouch for the site as a whole:
https://www.drstandley.com/food_whitefood.shtml
The main thing is to get rid of processed sugar, and of foods that are rapidly converted into sugars by normal metabolic processes. This isn't "all foods that are white", but many of the culprits are white or very pale (sugar, pasta, white rice, ...).
If you cut way back on sugar for a couple of weeks you lose the "addiction". When e.g. carrots start to taste sweet, you know your body is working the way it should.