There's a good post on that here for you.
I've put in a lot of work over the years to scale our lifestyle down. There is a very long list of things that I don't do, and of all the things that I do do, I do none of them perfectly. More like 30%-80%.
Pay special attention to making sure that diapers get changed on time; diaper rashes during survival mode are no fun at all.
The most essential essentials are food, clothing, and shelter. Probably the house will keep standing up on its own for a while, so that leaves food and clothing. And diapers.
Exercise: Even ten or fifteen minutes, twice a week, makes a big difference. Use weights (enough to challenge you at 5 reps, but not so heavy that you hurt yourself), and get physics on your side: Force = Mass x Acceleration, Work = Force x Distance, Power = Work / Time. In other words, use heavier weights, work up to fast but controlled movements, and do only a few reps of each motion before going on to the next.
Rest: Write it on your to-do list, because in survival mode you're too busy not to rest. Seize your opportunities as they arise.
UPDATED TO ADD:
Water: Pay special attention also to keeping your water intake consistent. If your hydration is all over the place, your blood sugar and mood and willpower and eating will be, too.