I saw this in action this month when I had my house painted. The estimate I received from the contractor was a very reasonable price, and he said that it would only take a weekend. In fact, the job took two weekends--effectively raising the costs to him as an independent contractor.
How does this relate to us in our profession? When we lose sight of the fact that time is a resource that requires management, we set ourselves up for the inevitable costs: money, morale, quality, credibility, etc.
If you are interested in taking a look at how you can be more effective with the time you have, browse through this slideshow on Time Management.