Sunk Cost Fallacy
The Fallacy
Keeping doing something bad just because you've already spent a lot of time on it.
Why it's wrong
If you are reading a boring book, you don't have to finish it just because you read the first half. You can stop!
Example
I ate half of this sandwich and it tastes yucky, but I have to finish it because I already started.
What the Fallacy?! (ELI5 Edition)