Everyone is going to say going to the gym and eating healthy, which are obviously how you stay healthy. But I think the key (to at least one of those) is having enough time in your day to make them priorities.

A big change I made a few years ago is getting up early. My alarm goes off at 530 and I'm at the gym by 6, workout till 715, then still have plenty of time to make a good healthy breakfast and take some "me" time before diving into work for the day.