You Ain't Gonna Need It or YAGNI is about not writing code that is not needed. I've gone on to realise how important this is when it comes to programming for change.
One of my biggest pet peeves that I have experienced working on agile teams is the excuse of YAGNI.
YAGNI is no excuse for doing a "proper job". The third step of the TDD cycle allows you to take the simplest thing that could possible work and refactor it into something more dynamic, flexible or just plain better.
If you spend your time writing the simplest thing possible such as brain dead procedural statements one after the next, the whole benefit of using TDD or writing automated tests is gone. You'd be more than capable of doing this yourself.
My discover here was simple. Don't skip the refactor part of TDD. Don't allow someone to play the YAGNI card. Do it right.