According to the Bureau of Labor Statistics, for four consecutive months ending in November, 2010 (the last month for which data exist,) more employees have been walking off the job than have been laid off. It really doesn't seem possible in a market where there are 15 million people unemployed.
This really speaks to confidence. However, it doesn't matter how confident you are. No matter how bad the job is, don't quit, unless you're being harrassed (in which case you should speak to an attorney,) until you've found another job.
Many people quit on a whim and think they'll start their own business. Not a good idea. It isn't easy to start a business in this economy. Make sure you've done your due dilligence. This takes time and lots of research.
Sometimes employees quit impulsively because they've simply had "too much" and they can't take it any more. Try telling that to your mortgage company or the credit card company when your payment is due. It doesn't work. If you leave your job, there'll be six people standing in line to take it, no matter how bad it was for you.
What I find just as interesting, is that management consultants agree that employers make a mistake thinking they can retain employees by dangling more cash in front of them. Research suggests that employees are more concerned and incentivized if they have a boss that cares; a boss that is mentor-like and helps the employee with their career.
If you're an employee and you hate your job, make sure you find another one before quitting. If you're a boss, make sure you're fulfiling the intrinsic needs of your employees; you may find their resignation sooner than later.