When you’re on military exercise, sleep is a luxury. Maybe you can only snatch a few hours each day. So there’s nothing so frustrating as lying in your sleeping bag with your eyes closed, waiting for something to happen.

You’re totally exhausted. You have to be up in three hours for picket. You’re distracted by the noises around you. There’s a rock jutting into your hip bone. Or you’re replaying the day’s events on repeat in your head.

If you don’t sleep, you’ll burn out pretty quickly. You’ll make bad decisions. You’ll let people down and become a liability.

That’s what happened with U.S. fighter pilots in World War II. The U.S. military realized many of its pilots were making terrible, avoidable decisions due to stress and the resulting sleeplessness. Shooting down friendlies. Being shot down themselves. Even when pilots clocked off, they couldn’t relax and they couldn’t sleep. So their stress and fatigue built up, till they made a fatal error.

No one wants to be that guy.

Luckily, you never have to be. The U.S. Navy Pre-Flight School developed a scientific method to fall asleep day or night, in any conditions, in under two minutes. After six weeks of practice, 96 percent of pilots could fall asleep in two minutes or less. Even after drinking coffee, with machine gunfire being played in the background.

Which means if you follow these steps, falling asleep will be a piece of cake.

Work with the real estate you have

Check out the available terrain. It might seem uninspiring, but that’s no problem. In fact, if you can stretch out at all, you’re already way ahead.

In the training, the pilots were taught to fall asleep while sitting upright in a chair. Which is a tough position to sleep in when you’re feeling restless. It’s why the airlines invented business class. But it was all the pilots needed. Sitting back in the chairs, they put their feet flat, and let their hands go limp against their laps. So remember a sleeping mat or room to lay down is a bonus. Work with the real estate you’ve got, knowing a humble seat will do.

Your face is the key to slowing down everything

Now that you’ve got your position, it’s all about the face. Think of it as the epicenter of your emotions. Close your eyes and breathe slowly and deeply. Then relax all 43 of your face muscles — no squinting or frowning. Your forehead should be smooth. Let everything go loose. Breathe out as you feel your cheeks, mouth, tongue, and jaw relax.

Your eyes are shut, but you want to make sure they are totally limp. Do this by letting them fall deep into your socket. There are six muscles that control your socket; feel them relax and go lifeless.

When you relax your face and let your eye sockets go limp, you signal to the rest of your body it’s time to unwind.

Send your upper body south

Now it’s all about the shoulders. Let them drop as low as they can, as if they were floating down your body. You should feel the back of your neck go lifeless. Let all the muscles there go even looser.

Breathe in deeply. Then exhale slowly, blowing out all of the tension.

Next are your arms. Start with your dominant side. If you’re right-handed, focus on your right bicep. Feel it relax and drop down your body. If it’s not relaxing, tense it first, then let it go loose.

Then move to your right forearm. Focus on sending it limp. Finally, comes your hand and fingers. Let them fall like a dead weight against your leg. When you’ve finished with your dominant side, work through the process with your other arm.

Your upper body should be nice and limp, like it’s sinking into you. You’re more than halfway there.

What to say to your legs

Next stop is your legs. Tell your right thigh muscle to sink, like a dead weight. Then tell the same thing to your right calf muscles. Then do the same thing for your ankle and foot. Feel the muscles go limp, as your leg sinks into the ground.

Repeat the process with the left leg, talking to your thigh, then your calf, then your ankle and foot.

Now you have unwound, relaxing every muscle in your body from your face to your feet. There’s just one more thing you need to do to turn your relaxed state into deep sleep.

How to not think about anything

The last step is to clear your mind for 10 seconds. That’s it. No thinking about what went wrong that day, or what time you need to get up, or when you’ll get to call your partner. Doing these things all involve movement. Which means just thinking about them is enough to make your muscles involuntarily contract.

Instead, you need to keep your mind still. You can do this by holding a static image in your head. Imagine you are lying on a comfy couch, in a pitch black room. Hold this image in your mind for 10 seconds.

If that doesn’t work, say the words “don’t think … don’t think … don’t think” over and over for at least 10 seconds. This will clear out any thoughts and stop your brain from wandering.

When you’re physically relaxed and your mind is still for at least 10 seconds, you’ll be asleep.