On the plane
Set your watch to DESTINATION time the moment you board, and behave by it: sleep if it is destination-night (eye mask, earplugs), stay awake and hydrated if it is destination-day. Skip the alcohol (it fragments sleep at altitude) and eat light on destination-meal rhythm. The plane is the first day of the adaptation — treat it as one.
Arrival day
Outdoor light within an hour of landing (the seek window), walk rather than nap, meals on local time, caffeine before 2 pm local only, and bed at local time even if the eyes disagree. The 20-minute nap is the maximum if survival demands one — longer naps donate the night's sleep pressure to the afternoon.
Days 2–3
Keep the light schedule (morning bright for eastward, evening bright for westward), exercise outdoors in the seek windows, and protect the bedtime with dimness. By day 3 on most eastward trips the mornings start feeling human; by day 4–5, the clock and the calendar agree. The schedule is boring; boring is what recovery looks like.