sleep

Get enough of it, and aim for the same times every day, regardless.

I don't really know what I imagined ever going into this category, so might as well start with the basics. Try to get eight hours a day and go to bed and wake at the same time, every day, seven days a week. If you go to sleep a bit late one day, don't try and sleep a bunch extra, just get up at your normal time.

• Stop using devices in the evening, way before bed.
• Dim the lights an hour before you go to bed.
• Have a cool, 16-18C bedroom.

Don't skip sleep, your body needs it. You are not as good a human without it.