> They're also effectively impossible to maintain consistently without medication.

This is key. As someone with bipolar disorder, I'm forever stuck in a cycle of stable with good habits -> episode happens -> can't keep the habits -> get worse -> medication changes/episode passes on its own -> I go back to good habits -> stable...

With mental illness you never know when it's going to act up and ruin your life, so the least you can do is use your energy - when you have it - to keep your body in a decent baseline.

Thankfully, this cycle takes many months to start again, so I live a decent life most of the time.