Choose reasonable over rational

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.

How to do it

1. When two plans compete, ask which one you’ll still be following after a bad year.
2. Permit small "suboptimal" choices that keep you calm and consistent (a little extra cash, a paid-off debt).
3. Treat your own temperament as a real constraint, not a flaw to override.

Evidence

Reflects findings that adherence and sustainability drive long-run outcomes more than theoretical optimality, and that loss aversion makes people abandon volatile-but-optimal plans. (mechanistic)

A reasoned principle drawing on behavioral findings; "reasonable" is deliberately judgment-based, so it resists precise measurement.

Sources

• 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.