Sunk Cost Is Already Gone
Does what you have already spent change what you should do next?
The idea
Money and time already spent cannot be recovered by any future choice, so they should not influence it.
In the real world
Two years invested in a failing project is a reason it hurts, not a reason to continue.
Going deeper
Money already spent is identical under every option available now, so it cannot distinguish between them. The only live comparison is what the next pound buys here against what it buys elsewhere.
The pull is not irrationality so much as the discomfort of making a loss concrete. While the project continues the £400,000 is still notionally working; stopping converts it into an admission. Recognising that continuing does not recover anything — it only adds — is what separates the emotional cost of stopping from the economic case for it.
Where it stops applying
Reputational and relational costs of abandoning a commitment are real and forward-looking, so they legitimately belong in the decision. What does not belong is the spend itself.
Why it matters
It separates the pain of stopping from the case for continuing, which are constantly confused.
Try this today
Ask of one commitment: would I start this today, knowing what I know?
Test yourself
A project has consumed two years and £400,000, and will need another £200,000 with a poor chance of success. Someone argues that stopping wastes the £400,000. What is wrong with that argument?
Show the answer
The £400,000 is gone under either choice, so it does not distinguish between them. The only live question is whether £200,000 buys a better outcome than spending it elsewhere. Continuing does not recover the past; it just adds to it.
Learn this in the feed Answering from memory, then again days later, is what makes it stick.