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Quick answers
What is mental accounting in one sentence?
Mental accounting is treating identical money differently by label — powerful for budgeting goals, costly when labels block net-worth logic.
Is this financial advice?
No. Tool-Lifes pages are educational atlases. Decisions need your goals, constraints and, when appropriate, a licensed adviser.
Do I need a high return for compounding to matter?
Higher net rates help, but time and contributions often dominate — especially early. Costs and behaviour can erase a “good” rate.
How should I use the calculator?
Treat outputs as scenario sketches. Vary contribution, rate, fees and inflation to see which lever moves your goal date.
What about inflation?
Always ask whether a figure is nominal or real. A high nominal path can still lose purchasing power.
Are past returns a promise?
No. Illustrations use round teaching numbers. Markets, inflation and taxes change.
Most damage is mundane: fees ignored, inflation forgotten, contributions paused, or a plan abandoned in a drawdown.
Treat the list as an error budget — pick the failure modes you are actually exposed to.
Traps
- Gross-return shopping — Comparing products on advertised yield without fees, taxes or risk.
- Horizon mismatch — Using long-equity math for a two-year house deposit.
- Contribution droughts — Stopping buys after a raise, a crash or a boring year.
- Yield spending — Treating dividends as free income while needing growth.
- Complexity cosplay — Options and themes that mainly add costs and decision fatigue.
Myths
- “Compounding needs a secret rate” — Time and contributions often dominate cleverness.
- “Cash cannot lose” — Inflation and opportunity cost are real losses of purchasing power.
- “Past decade = next decade” — Regimes shift; process beats narrative extrapolation.
- “Apps remove all risk” — Automation removes some behaviour risk, not market risk.
Fixes
- Write the job — Label each pot: buffer, medium goal, long engine.
- Automate C — Payroll or app transfers beat monthly willpower.
- Cap costs — Know all-in TER + advice + FX spreads.
- Pre-commit rules — Rebalance bands and drawdown behaviour written when calm.
Pitfalls are usually process failures. Repair the process before hunting a new product.