A plan is an example of what could happen, not a prediction of what will happen.

I don't like the feeling, but I've got to say that a little fear makes me a more focused, more responsible programmer.

I tell people to start implementing when they are pretty sure there aren't more important stories out there. An iteration's worth of data is worth months of speculation.

The system metaphor is a story that everyone--customers, programmers, and managers--can tell about how the system works.

If you're having trouble succeeding, fail.

How good the design is doesn't matter near as much as whether the design is getting better or worse. If it is getting better, day by day, I can live with it forever. If it is getting worse, I will die.

Sometimes the problem has to mature before the solution can mature.