You wanna avoid falling asleep or passing out so, if you can, stop and get a red bull 5 hour energy coffee crack (KIDDING) well not really, but a good thing to do to is avoid positions where you're lying down.
Positions like her on top or side to side; so get active and go crazy...not lazy.
To keep yourself awake try switching up positions throughout the night and try as best as you can to be on top or behind. It's harder to pass out from these position.
As a woman, I'll tell you there is nothing more embarrassing than giving away your goodies to a guy that's passed out and snoring.