Trust your heart and instincts BUT do your homework! Know you have something unique and interesting, including looking at your bookshelf peers upfront. Get a good editor and involve them earlyish in the process. Get a good book cover designer and be professional in your approach at all times. Do your research - fiction or non-fiction - because this adds detail, insight and builds your story. Avoid letting the editor drown out your voice with mechanically correct prose and grammar! Realise that your journey today only just begins once you publish and you are going to need to become a marketeer/promoter and publisher and you will need to ride a step learning curve. But hey i´m not a successful writer yet so who knows!