Three weeks without food
Last but not least is the ability to acquire food. Whether that being hunting, trapping or butchering methods or storing food(or seeds for gardening) for emergencies. There are many excellent references out there and you have to do your own research to find which will work best for you.
One thing to take into account is that when hungry your judgment can get cloudy causing you to make mistakes that can jeopardize your well being.
Another thing to mention is that sleep is necessary along with a positive attitude to make the right decisions and to think on your feet as the priorities can change depending on the circumstances.
In conclusion I can't even begin to touch this subject, there are no givens and the ability to think on your feet and make sound logical decisions will take you far.
One time a piece of machinery broke at the farm and my wife finally became annoyed at how long it was taking for the repair. She asked " Do you know what your doing" My reply was " Hell no, I just make it up as I go".
And that's what you'll have to do.
In my opinion two of the best references I've read covering these subjects are 98.6 Degrees and When All Hell Breaks Loose both by Cody Lundin.