Starting a business isn't risky -- it's about managing risks. It's good that you're seeing risks now, before you launch your business! That's what's supposed to happen. Your planning activity's goal is to discover how you'll manage and reduce those risks. Then, when you launch your business, your risk level will be low.
Opportunities have changed since this post was started. No longer do you need to quit your job to create a business. You can start smaller--on a micro level. Become an expert in your field using the vast and varied technologies available on the internet.
10 years ago, I started a business the old fashioned way. I invented a product, did all the development, turned the idea into a boxes and boxes of inventory in my garage. As a stay-at-home mom, I thought the website I paid $5000 to have developed would help me sell. I didn't realize I still had to do all the work. I eventually licensed the product and closed up shop. Invested several thousand dollars and though the product never made money, I still consider the experience invaluable.
Fast-forward to now. I'm still a stay-at-home mom, but I am now using the internet to start a new business. This time following the start-small, dip your toe in, approach. The ability to promote my business via the internet has expanded, web sites are easy to develop, and I can truly test the waters without sinking the ship.
So that's my advice to you wanting to start a new business...test it out first. Take one step at a time and go where the business takes you, but don't quit the paying gig until the experimental steps show positive results.
In my case me and a couple of friends started our business. It was quite intimidating at first but its also partly fun. Watching your investment go down the drain and so on. but we did managed to survive it. :D
Starting a business is always very scary, especially if you're giving up a decent and secure job. One of the ways of getting rid of this fear is to prepare and research the business you are going into. Write down all the reasons why you want to start a business to begin with, and study it carefully. By reading it, it will make it more real and help you realize why you want and/or need to do this. You will also need to learn how to deal with your fears, this will take time but the more you work on it the easier it will become. Know that your fears are normal, and this is what most people feel before starting a new business so you are not alone with this.