Money
Pricing, margin, and what a thing is actually worth.
Extraordinary Outputs Require Extreme Inputs
If your goal is extraordinary, the advice to live a balanced life was not written for you. Why starting late on financial independence takes an extreme input, and how to sustain it.
Diminishing marginal utility
Each additional unit of something is worth less than the one before it. The first slice, the first thousand dollars, the first hour of free time are worth more than the tenth, and the decline is usually steeper than people expect.
Relative deprivation
Dissatisfaction produced by comparison with a reference group rather than by conditions themselves. People asked how they are doing answer relative to whoever they are standing next to, and the reference group is rarely chosen deliberately.