YAGNI is the acronym for the You Ain't Gonna Need It principle. It aims to erase all unnecessary code and focuses on the current functionalities, not the future ones. The less code you have, the less code you're going to maintain and the lower the probability that bugs will be introduced.

For more information on YAGNI, visit Martin Fowler's article available at http://martinfowler.com/bliki/Yagni.html.