Hi there, readers. You step off a 12-hour flight, the clock on the wall says it's mid-afternoon, and your body is convinced it's the middle of the night.

That gap between where you are and where your internal clock thinks you are is what you'll spend the next few days fighting, and how you handle the first 24 hours matters more than anything you do on the plane.

Set your clock before you fly

The adjustment starts before you board, not after you land. A few days out, shift your sleep and meal times toward your destination's schedule by about an hour a day. If you're flying from New York to London, that means going to bed and waking up earlier so the five-hour jump feels smaller. Book a flight that lands in the morning or early afternoon if you can, because arriving at night tempts you to collapse, and that's the fastest way to stay stuck on the wrong clock.

Use light as your reset button

Sunlight is the strongest signal your body has for resetting its internal clock. When you land in the morning, get outside within the first couple of hours, even for a 20-minute walk. Your eyes take in the daylight and your brain starts shifting its schedule. If you've flown east and you're dragging by late afternoon, stay outdoors as long as you can to push through. Flying west is easier for most people, but the same rule applies: get light when it's daytime at your destination, avoid bright screens late at night.

Sleep on local time, not your body's time

The hardest part is the first night. Your body will want to wake up at 2 a.m. and you'll be wide-eyed staring at the ceiling. Resist the urge to get up and start your day. Stay in bed, keep the room dark and cool, and try to sleep until a reasonable local morning. A short nap is fine, but cap it at 20 minutes and never after mid-afternoon, or you'll rob yourself of the sleep you need that night. Melatonin, taken about 30 minutes before your target bedtime, is commonly used to nudge the clock along, though it works better as a small push than a fix on its own.

Eat and move on the new schedule

Meals are another clock signal, so eat at local meal times even if you're not hungry. A light breakfast at 8 a.m. local time tells your body the day has started. Stay hydrated and skip heavy meals on the first day, since digestion runs on its own rhythm and a big late dinner can keep you up. Get some gentle movement in, a walk or a swim, but don't exhaust yourself with a hard workout when you're already running on little sleep.

The first day is the one that counts. Get outside, eat when the locals eat, and hold your sleep until a normal local bedtime. Do that and you'll shave a day or two off the fog. Next time you land somewhere far from home, remember: the sun and the clock on the wall are your two best tools, so use them early and let your body catch up.