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Concept

Reasonable Over Rational

Reasonable over rational is Morgan Housel's principle that the best financial plan is not the one a spreadsheet calls optimal but the one you can actually live with, because a strategy you abandon in a bad year earns nothing.

Financial theory assumes a cold calculator who cares only about the highest expected return. Real people also care about sleep, family arguments and regret, and Housel argues in The Psychology of Money (2020) that ignoring those feelings is not discipline but a design flaw. A plan that is mathematically optimal and emotionally unbearable tends to be dropped at the worst moment, usually after a fall, and an abandoned plan earns nothing. A plan that is slightly weaker on paper but feels right is the one that survives the years compounding needs. A widely reported story about Harry Markowitz, whose work laid the foundations of modern portfolio theory, makes the point: he said he split his own retirement savings evenly between shares and bonds, not because his model required it but to limit the regret he would feel either way. Being reasonable does not mean being careless. It means admitting in advance which choices you will not be able to keep, such as a portfolio that swings too hard, a budget with no room for pleasure or a debt that keeps you awake, and building those feelings into the plan instead of pretending they will not appear. The test is endurance, not elegance.

A real-life example

Emre, a pharmacist in Bursa, read that a young investor should hold almost everything in shares. He tried it, and in his first sharp fall he opened the app twenty times a day and sold half at a loss. Now he keeps a larger slice in a deposit account than any calculator would recommend and puts a fixed 3,000 lira into a share fund every month. He gives up some return on paper, but he has not missed a monthly order in three years.

How to use it

  1. 1Write down the plan a calculator would choose, then mark every part you doubt you could keep through a bad year.
  2. 2Adjust those parts until the plan feels bearable on your worst day, even if it costs some expected return.
  3. 3Judge the plan by whether you are still following it in five years, not by its return in the best case.