The Mythical Man Month

is the title of an excellent book by Fred Brooks. It's well worth rereading every year or so. As usual I'm going to quote from a few pages:
The accumulation of simultaneous and interacting factors brings slower and slower motion.
Human beings are not accustomed to being perfect and few areas of human activity demand it.
Our estimating techniques fallaciously confuse effort with progress.
No part of the schedule are so thoroughly affected by sequential constraints as component debugging and system test.
Take no small slips... Trim the task.
I will contend that conceptual integrity is the most important consideration in system design.
...the total creative effort involves three distinct phases: architecture, implementation, and realization. It turns out that these can in fact be begun in parallel and proceed simultaneously.
Any software system should be grown by incremental improvement... Nothing in the past decade has so radically changed my own practice, or its effectiveness.
Unless we teach people how to design, the languages matter very little.
The Mythical Man Month is only incidentally about software but primarily about how people in teams make things.