IMO developing good sleep hygiene is by far the most important habit to cultivate.

It has lots of benefits, but the most important one is it replenishes your willpower. If you're trying to develop other healthy habits, it's 10x harder if you haven't slept well.

"eat healthy food as much as possible."

I usually stop, if my body signals me I had enough.

(might seem like pedantery, but I know some people do believe it literally, that it is healthy to just fill themself up with "healthy food", but it is not).