Describe something you do to stay healthy.

The habit I'd like to describe is my morning walk — thirty to forty minutes, every day before work, which I've kept up for about three years now.
It started, as many good habits do, from a bad place. During a stressful project I was sleeping badly, eating at my desk, and a routine health check produced numbers that frightened me. I knew myself well enough to skip any dramatic plan — no gym memberships, no radical diets, because I'd abandoned both before. Instead I picked the most boring possible intervention: leave the house at seven, walk one loop of the local park, come back.
The genius of it, if I can call it that, is that it's too easy to fail. Rain? I have an umbrella. Tired? It's only walking. Because the bar is so low, the streak survived, and after a few months it stopped requiring willpower at all — it's simply what mornings are.
Why does it work? Partly the exercise itself, but I suspect mostly the knock-on effects: I sleep better because of the morning light, I eat breakfast properly because I'm awake earlier, and I arrive at work with my head already sorted. My health numbers quietly normalised within a year. It's the highest-return thirty minutes of my day.