November is fast on the way, and if you've always said, "I ought to write a book one day" - why, now's your chance!
National Novel Writing Month (or NaNoWriMo to use Internet-speak) challenges aspiring writers to write a 50,000-word novel in a month. It sounds tough but it can be done.
So go on, give it a try. Yes, nothing may come of this novel. Does that matter? You'll have done what many people say they will do but never even attempt. There are few things as satisfying as finishing a novel, and that's especially true of the first.
You may like what you've done well enough to take the next step. Edit, revise, edit again. Show it to those whose opinions you respect and find out what they think. (Remember, you can't go directly from NaNoWriMo to being published!)
And who knows, you may even decide to write another novel! (You know what they say - First one's free!)
Go on and do it. You know you want to!