You ain't gonna need it

You ain't gonna need it, or short YAGNI, suggests to programmers that they should not add functionality until it's necessary.

Ron Jeffries, one of the 3 founders of Extreme Programming Software Development Methodology, states: "Always implement things when you actually need them, never when you just foresee that you need them." According to him you often will hear yourself saying: "We are going to need..." Just resist that impulse and stick to the essential functionality.

"The best way to implement code quickly is to implement less of it. The best way to have fewer bugs is to implement less code."[xp]