Why the Best is the Enemy of the Good?

Are you an entrepreneur and need some motivation, specially during these tough economic conditions?. Then How successful people win by Ben Stein will be a good read.
Ben states 10 rules for everyone to win in their game and each one of them were gold.
Some of the them are:

1. The Best is the Enemy of the Good
2. Nothing Happens by Itself
   
3. The One Indispensable Ingredient - Persistence

He goes in detail about each rule, with an example.
Often, times like these, will test our strength and books like these will help to make us more stronger.

What is your favorite book?