According to all the statistics it is much more likely for your first business to flop than to succeed. This should not prevent you from trying, though. Just like Neo falling the first time - everybody falls the first time (comparison is great and is not my idea - saw it on some blog the other day, unfortunately forgot where).

More along these lines can be found in No one starts with a masterpiece. I'd like to add a bit to the theme... not only that (quote from the post) No one actually knows what they’re doing but also no one throws away their first product, even when it fails.

I cannot emphasize this enough. The work you do for your first product will be reused later, even if sliced into pieces and re-assembled into something completely different. No one works in vacuum - if nothing else, business contacts, payment processor, work habbits, and most importantly your source code will give you a big head start in your second business (unless you succeed the first time but then all this is irrelevant anyway :)). The experience you get while trying is absolutely crucial - it's very unlikely you'll repeat any of the mistakes you might have made on your first try.

In other words, just do it and worry later. Here's a motivational example - did you know that the company behind FolderShare  (recently [November 2005] acquired by Microsoft) is the same one that used to do music sharing service Audiogalaxy? I remember downloading some of the music (illegaly!) over the Audiogalaxy during the early P2P days (when Napster still ruled). I think it is very reasonable to assume that P2P technology developed for Audiogalaxy wasn't just thrown away and that FolderShare is a direct descendant of that code.