Neil Patel wrote an interesting post about how much experience should you have before going out on your own. In other words, how much time spent walking is needed before you can actually run?
Neil says he didn't really walk at all when he first started out and failed as a result. However the education he gained in trying was worth "millions."
My opinion is that you need to have a general idea of how to proceed before doing so. I don't mean 5 years interning (or whatever) at some corporate office before going out on your own. More like a lot of reading and some rational planning. Everything else is just guts and making correct decisions quickly.
Your personality will play a role in your success as well. People who are more assertive generally are able to make things happen easier. They aren't afraid to ask for — or demand — what they want. While that seems easy, it's a little more difficult for most people. Myself included.
Other personality traits will come into play as well. Are you a social person or more of a recluse? Obviously this can play a role in your real life networking, which is a part of practically any business.
Discipline is very important. It is one thing to manage other people but it is a much harder task to manage yourself. Are you able to stay focused and motivated when it really matters? We all find ourselves distracted during the day. Email, IM's, RSS feeds, etc. all cause us to take a break many times a day. This break also takes you out of the "zone" when you are focusing on actual work. You must be able to avoid, or limit, those distractions as much as possible to ensure that you are getting your job done. Your success can (does?) depend on it.
Confidence can make or break you and your new venture. You have to truly believe in yourself and your idea/product. Lack confidence and you might as well wear a sign saying so. It's already written all over your face anyways. If you don't feel confident in yourself, why would anyone else?
I feel that if you prepare and plan correctly then give yourself a real gut check, you have a good shot at making it. Walk a little before your start to jog. Get a good pace and begin to run!
P.S. The comments on Neil's article have many good opinions. I suggest you read them.