"The important point is that the cost of adding a feature isn't just the time it takes to code it. The cost also includes the addition of an obstacle to future expansion. Sure, any given feature list can be implemented, given enough coding time. But in addition to coming out late, you will usually wind up with a codebase that is so fragile that new ideas that should be dead-simple wind up taking longer and longer to work into the tangled existing web. The trick is to pick the features that don't fight each other."

John Carmack

Make all the important information visible in one place and then decide what to do together. 

~ Henrik Kniberg

Any improvement to the software delivery process should speed up the rate with which we deliver value, not the rate with which we burn effort. For as long as we only track inputs – effort, story points, number of tasks – we’re essentially tracking time.

~ Gojko Adzic