A: Write because you love it, write for yourself, and write every day. And if you can make money at it … all the better.
On a more technical level, work with beta readers and editors who will give you actionable feedback that helps you improve the story you’re working on — and your craft — in very specific ways.
If you’re getting feedback like, “oh, I like that” or “eh, I didn’t get it,” then they’re not really helping you.
Be highly selective, choosing people who will tell you what you actually need to hear, not what you want to hear. And keep your world of trusted ‘advisors’ on the small side. Feedback from too many people will distract and confuse you.
Ultimately … only you can decide what having “success” means to you. There’s lots of disappointment and rejection in being an author, so having a healthy sense of self-worth and realistic expectations will go a long way towards keeping your sanity.
Remember that once you’ve finished your novel and, if it’s published, you are no longer in ‘author’ mode, but in ‘retailer’ mode. You’re trying to sell your books, and that’s an entirely different skill set and experience than writing.
That’s why it’s important to try to manage your expectations and define how you define success.
Being an author is a lot of work, so try to have as much as you can along the way.