A clean quantitative framing is this: tax-loss harvesting is a timing tool, not a wealth tool. Mechanism: When you sell a losing position to offset gains, you are deferring taxes, not eliminating them. The deferred tax becomes a zero-interest loan from the government. Why it matters: That matters because investors sometimes treat harvesting as free return when it is really a cash-flow advantage that benefits long holding periods. Market translation: Selling a $10k loss to offset $10k of short-term gains at a 35% bracket defers $3,500 in taxes. The value depends on what you do with that capital between now and eventual realization. Failure mode: The mistake is harvesting indiscriminately without checking wash-sale rules or whether the replacement position changes the portfolio's intended risk profile. Review question: Before sizing up, identify whether the edge comes from cash flow, volatility, timing or balance-sheet structure. That is the kind of small conceptual habit that compounds into better decisions over time.