The Pragmatic Programmer

by Andy Hunt

The early bird might get the worm, but what happens to the early worm?

Don't be a slave to history. Don't let existing code dictate future code. All code can be replaced if it is no longer appropriate. Even within one program, don't let what you've already done constrain what you do next—be ready to refactor (see Refactoring, page 184). This decision may impact the project schedule. The assumption is that the impact will be less than the cost of not making the change.[1]

As a program evolves, it will become necessary to rethink earlier decisions and rework portions of the code. This process is perfectly natural. Code needs to evolve; it's not a static thing.

Don't try to refactor and add functionality at the same time. Make sure you have good tests before you begin refactoring. Run the tests as often as possible. That way you will know quickly if your changes have broken anything.