Stay awake for seventy-two hours and you will learn to write instructions down and work them step-by-step checking each action off AFTER you complete it.

Verbal instructions don't work well when everyone is exhausted because short-term memory evaporates and they forget the first step before you finish telling them the second. So you write instructions down and have them work the list.

Lack of food, water, stress, and pain make this problem worse.

A small notebook, typically a 3by5 flip-top, is your brain in the field. You have lists of standard SOPs, times, places, frequencies, call signs, mission priorities, notes on the route you took and shorthand reminders of alternatives. You don't rely on memory for anything of consequence.