Plan to throw one (implementation) away; you will, anyhow.

The first step toward the management of disease was replacement of demon theories and humours theories by the germ theory. That very step, the beginning of hope, in itself dashed all hopes of magical solutions. It told workers that progress would be made stepwise, at great effort, and that a persistent, unremitting care would have to be paid to a discipline of cleanliness. So it is with software engineering today.

System debugging, like astronomy, has always been done chiefly at night.

You can learn more from failure than success. In failure you're forced to find out what part did not work. But in success you can believe everything you did was great, when in fact some parts may not have worked at all. Failure forces you to face reality.

The Waterfall Model is wrong and harmful; we must outgrow it.

Design work doesn't just satisfy requirements, it elicits them.

A basic principle of data processing teaches the folly of trying to maintain independent files in synchonism.