The New XP "...nature continuously uses fractal structures, which are similar to themselves but at various scales. The same principle should be applied to software development: we should be able to reuse similar solutions, in different contexts."
Or as Greg says, "Only by pursuing code reuse in the small will you ever achieve code
reuse in the large."
"Software defects must be looked for, found and fixed in many ways (pair programming, automated testing, sit together, real customer involvement, etc.). This is redundant, because many defects will be found many times. However, quality is priceless."
"...quality must be always at maximum. Accepting a lower quality does not yield neither savings, nor faster development. On the contrary, improving quality necessarily makes an improvement of other system features, like productivity and efficiency. Moreover, quality is not only an economic factor. Team members must be proud of their work because it improves team self-esteem and effectiveness."
"It is easy to order to developers “Do this”, or “Do that”, but it does not work. Unavoidably, you ask less than what could be achieved or, more likely, more than that can be accomplished."