Sleep. The secret to keeping a crazy schedule is to never let yourself feel fully rested.
Wake up in the morning at the crack of dawn. Get dressed, hop in a car, and drive to the school. Check out a grip truck, and then drive it to set, barely arriving by call time. Spend six hours lifting heavy equipment, hot lights, and pushing the dolly around. Break for an hour for lunch. Six more hours of heavy lifting, hot touches, and dolly pushes. Wrap all the equipment back to the truck. Drive the truck back, check in the keys, and drive home. Eat dinner, shower. Spend at least an hour writing, because that's what you do when you want to be a writer.
Then there remain five hours until you have to wake up and do it all again the next day. Those five hours are blissful and some of the best sleep you can get.
This might be an extreme example, where I sacrifice sleep because I don't have those other things to sacrifice, but I find that sacrificing sleep is always more advantageous to me than sacrificing going to see a movie or even just staying home and Netflixing a movie. Watching movies is critical to my development as a filmmaker; pushing all that aside will stunt that growth, and if that's the case then why am I doing all this other stuff?
It's all about priorities. There's never a "right" thing to sacrifice in order to get work done; you do what you have to, and that's that.