Starting with a good long brainstorming session helped me. The first day of the jam, I was meant to go out with friends - I thought about cancelling, but instead, took the time driving there and back to think up ideas. I used a Trello board to write everything down in two lists - must haves, and things to do if I have time. I concentrated on the must-haves first and made sure I had a playable game within the first couple days. Everything else was adding as much fun fluff as I had time for! This is all juggling my normal job, as I'm sure many of us were.
I also kept a timer on the desk and made sure to stand up and move around or get on the treadmill for a few minutes every half hour or so. Plenty of sleep, no skipping meals.