Economics
The tenth slice of pizza never feels as good as the first
Each additional unit of something you consume tends to deliver less added satisfaction than the one before it — the first cold drink on a hot day is transformative, the fifth barely registers. Economists used this to explain why demand curves slope downward and why a fixed sum of money matters more to a poor person than a rich one, since each extra pound buys progressively less added wellbeing. It's a foundational building block of modern consumer theory.