Humans are animals in the environment, not on top. We have certain physical requirements that nature haas designed us to achieve, nature has provided the nourishment for us and like all other animals, we require sufficient sleep to conduct repair and recovery - essentially preventative maintenance.
When chaos hits, the levels of uncertainty, lack of sleep, nutritional interruptions and general anxiety will tax your physical health. That is why it is the first thing we recommend addressing in adopting a prepared life.
Simple: exercise for function, eat food that nature provides and get at least 6 hours of sleep.
Physical, like your mental and financial health is a continuous improvement system, once you begin the journey to better health, you can then and only then, consider supplies, skills and more traditional preparedness ideas.