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LESSON 5 · Your Irrational Brain: Behavioral Economics

Sunk Cost in Relationships

The fallacy reaches far beyond money. People stay in unhappy relationships partly because they have invested years of emotional energy that would feel wasted if they left.

The reasoning sounds logical: we have been together seven years, so leaving now wastes all that time. But those years are gone regardless. The only relevant question is whether the next seven years will be better spent together or apart — a question sunk costs cannot answer.