What do you think it takes to succeed as a novelist -- not just to get that first contract, but to build a career? In order of importance, here's what I think:
1. Talent -- without this spark, you won't get anywhere. Hard work will make you better, but without SOME talent, I don't think you can write novels anyone will want to read.
2. Hard work/discipline -- that talent does have to be supported, consistently supported, by what Jane Yolen calls BIC (butt-in-chair).
3. Good judgement -- about yourself, your talent, the business: knowing where to put your energy. Some people don't need this -- what they're best at and most interested in writing and the marketplace all align nicely; but (I think) many of us face hard decisions....and even those fortunate few need to decide whether, say, promoting their books is a good or bad use of their energy and time.
4. An editor who really loves and GETS your work.
5. The fortitude to conquer your demons or the good luck to not have any.
6. SOME luck -- at the beginning, to get a good agent (thank you stars and Sara!) and maybe even to get your novel read and published? Later, if you aspire to making it big, luck will definitely be needed for that. The linked essay by isn't about making it big, but the story of how his first book became a bestseller is a good (and unusually frank) example. I'm not saying that all it takes it make it big is luck -- the book needs to appeal to lots of people, too! -- but which of the good books published each year become blockbusters does depend as much upon luck and timing as merit and promotion, particularly if the author is unknown.
7. The support (if financial, so much the better!) of family or friends or both.
8. If you want your work to last: something to say. By "something to say" I don't mean a simple lesson, but the sum of what your novel says/means -- something only you could have said in that way. I put this last not because I think it is the least important but because I think it's quite possible to be published, and even build a successful career, without it. But the books that people are still reading a hundred years later all have it -- and maybe many we AREN'T reading a hundred years later have it too. Luck again?