Simplicity
With constant pressure to add features and options and configurations, and to ship code quickly, it's easy to neglect simplicity, even though in the long run simplicity is the key to good software. Simplicity requires more work at the beginning of a project to reduce an idea to its essence and more discipline over the lifetime of a project to distinguish good changes from bad or pernicious ones. With sufficient effort, a good change can be accommodated without compromising what Fred Brooks called the 'conceptual integrity' of the design but a bad change cannot, and a pernicious change trades simplicity for its shallow cousin, convenience. Only through simplicity of design can a system remain stable, secure, and coherent as it grows.
(Preface, The Go Programming Language)