Management sage and scholar, Peter Drucker used to teach that the best business managers compartmentalized the fear of getting laid off and instead used that energy toward making calculated decisions to improve business performance. It is a pretty incredible thought to act and work without the fear of a layoff. Most people don't act or work that way. They certainly allow fear to influence their actions.
The bigger question is what to do when you are laid off. This is a complex question and requires your deepest thinking and broadest networking efforts. I think Dr. Cohen lays out an excellent strategy in a recent Business Week blog post.
Check it out.