Just write!

I've often wondered about the great authors of the past. About whether they knew they were writing something that would be viewed as great. Did they believe it would be great, or did they hope? I know that Tolkien never expected to be published. I also know that he was 62 when the first part of The Lord Of The Rings was published in 1954. What on earth happened (or not) that it took that long? Well, he was married with a family, he was a professor of English, delivering classes and lectures, he wrote other stuff including The Hobbit, so it can be seen that he lived a very full life. Although he couldn't have foreseen the effect his work would cause from the 60s onward, I would hazard a guess that his preparation in life was leading to it. Tolkien was working on a great piece of writing - consciously working on what he subconsciously believed was a great work. It is the only explanation I can give for his writing of the epic and beautiful story he wrote for us. He couldn't know, but his subconscious did, his instincts did.
How about his contemporary and friend C. S. Lewis - did he know how great his own work would be viewed? When we speak of The Chronicles Of Narnia, did he believe that people would speak of it as they do? And how about J. M. Barrie? Or Lewis Carroll?
Dickens? Now here is a writer who wrote a lot of things, brilliant things.
And in the modern world, how about Iain Banks, or Dean Koontz?
Is it belief, confidence, or hope? Modesty would say hope, or even belief. Definitely not confidence - no-one can be confident that they are writing a great work. The thing is that you go ahead and try. Something is telling you that you must try.
Self-doubt, of course, can and will creep in. There may be less of it if you are already published, or have been given a guarantee of publication, but it will creep in with its own depth at some point. That is a human reaction - a subconscious kick in the pants not to let your standards drop. If you have ability, I don't believe it is a self-doubt about your own ability. It is an instinctive, subconscious reminder not to let your standards drop. Failure is only a complacent pen-stroke away.
I think you have to believe you are a writer. I think you have to do the preparation which will help ensure that you are shown as a writer. I think you have to follow your own muse and write what you believe you should write - hopefully, that should ensure the individuality of your work, and help you to stand out from the crowd. I think you should listen to your contemporaries - it's a rare contemporary who would wish you ill-luck, or deliberately give bad advice, and you will know these people, or your instincts will, for sure. You need support - all of the greats have had their critics: Tolkien, Dickens, Keats to name a few, have all taken shots to the heart. Why shouldn't you? And you only have to witness the criticism levelled at JK Rowling to know what's coming whether you make it or not.
In short, I believe that you should do what you feel you should do. As best you can. Believe in yourself. The rest, for good or bad, is out of your hands. Why worry about that?