A margin of safety is a recognition that you may be wrong, and that the world is complicated. It is a recognition that even with perfect understanding, ever present randomness means you will never be fully in control. Never put the things that matter most at risk because of the things that matter least. A buffer provides the ability to look up from the task at hand. Enough to eat for the week means you can think about what to eat in a month. Relationships start with a buffer of things in common that earn you the right to develop.