Choose reasonable over rational
A plan you can stick with beats an optimal plan you’ll abandon.
Key takeaways
- What it is: A plan you can stick with beats an optimal plan you’ll abandon.
- Why it works: A mathematically optimal strategy you can’t emotionally sustain has a real-world expected value of zero, because you’ll bail at the worst moment. "Reasonable" decisions — ones that let you sleep and stay the course — outperform "rational" ones in practice because durability, not theoretical optimality, is what captures long-run results.
- Evidence: Plausible mechanism, limited direct outcome data.
- Avoid: Optimizing on a spreadsheet for the highest expected return, then abandoning the plan in the first downturn because it was never emotionally survivable.
Why it works
A mathematically optimal strategy you can’t emotionally sustain has a real-world expected value of zero, because you’ll bail at the worst moment. "Reasonable" decisions — ones that let you sleep and stay the course — outperform "rational" ones in practice because durability, not theoretical optimality, is what captures long-run results.
How to do it
- 1When two plans compete, ask which one you’ll still be following after a bad year.
- 2Permit small "suboptimal" choices that keep you calm and consistent (a little extra cash, a paid-off debt).
- 3Treat your own temperament as a real constraint, not a flaw to override.
What the evidence says
MechanisticReflects findings that adherence and sustainability drive long-run outcomes more than theoretical optimality, and that loss aversion makes people abandon volatile-but-optimal plans.
Honest caveat: A reasoned principle drawing on behavioral findings; "reasonable" is deliberately judgment-based, so it resists precise measurement.
- — Behavioral economics on loss aversion (Kahneman & Tversky) explaining why people abandon volatile optimal strategies
Common mistake
Optimizing on a spreadsheet for the highest expected return, then abandoning the plan in the first downturn because it was never emotionally survivable.
IX Coach factors your actual temperament into the plan, helping you pick the version you’ll keep — and flags when "optimal" advice is one you’re likely to quit.
Practice this with IX Coach →