Have you tried APing while sitting up or sitting in a chair?
If you conk out, you're body will jolt you awake enough to balance between those states conductive for APing. (The bigger the passing out, the bigger the jolt).
Developing concentration also helps in staying awake, too much though you may feel jittery, restless(wide-awake), too little..fall asleep. Focusing in on a point will help keep your mind occupied as you let your body fall asleep(or reorient focus to non-physical).
Basically is what you may be trying to do is retrain your mind/break a habit(falling asleep, or sleeping unconsciously), once you break the habit of unconscious sleep, APing at will is effortless(since you will be aware of the process thus circumnavigating it).
Anyway, that's what helps me, I'm sure more people will chime in with what helps them and soon enough you'll be APing rightly.