I picked up a Shaker proverb from Ryan Davis at a recent nyc.rb meeting. It applies splendidly to software development:

If it is not useful or necessary, free yourself from imagining that you need to make it.

If it is useful and necessary, free yourself from imagining that you need to enhance it by adding what is not an integral part of its usefulness or necessity.

If it is both useful and necessary and you can recognize and eliminate what is not essential, then go ahead and make it as beautifully as you can.

– Shaker saying (“Shaker Built: The Form and Function of Shaker Architecture” (This origin is dubious)