What does it mean that the sunk cost trap in commitments?

Past investment does not justify continuing a commitment that no longer serves you.

Example: You have spent two years building a side project — evenings, weekends, savings. The technology shifted, the market moved, and honest assessment tells you the project has no realistic path to the outcome you originally wanted. But every time you consider walking away, your mind calculates the cost: 700 hours, $4,000, relationships you neglected to make time for it. So you keep going. Not because the future looks promising, but because the past feels too expensive to abandon. You are not investing in a project anymore. You are paying rent on a sunk cost — and the rent is your present-tense life.

Try this: Identify one commitment you are currently maintaining primarily because of what you have already invested in it — time, money, reputation, emotional energy. Write down two lists side by side. List A: everything you have already put into this commitment (the sunk costs). List B: what continuing this commitment will realistically produce in the next 6 months, assuming the same trajectory. Now cover List A with your hand and read only List B. If a stranger saw only List B, with no knowledge of your history, would they advise you to start this commitment today? If the answer is no, the sunk cost is the only thing holding you in. Name that honestly.