Advice for newly published writers

(And oldly published writers, and yet-to-be published writers, too - basically whoever is willing to take advice from an eighteen-year-old)

1. Do not read your reviews, good or bad. Remember: reviews are for potential readers, not for you, the author. Leave the review reading up to your editor or publicist or grandparents or whoever. Your work should already have been ripped apart by about ten different people prior to publication, and reviews will not tell you anything you do not already know. You cannot convince people who hate your work to love it, and you will never be able to get quite enough praise from those good reviews. Don't go down that path! That path leads to no good things! (I say absolutely do not read your reviews because I know you will read a few anyway. They are very easy to look up and very difficult to resist.)
2. Forget about rubbish like 'personal brand'.  I know everyone says things like 'your book is not the product you are selling, you are the product' but really, if you think too much about yourself as a packaged, constructed thing, then you will go mad. Just be generally nice and supportive of other people, and don't badmouth anyone, and don't write a blog full of swear words if you write for children. It's pretty straightforward. People who are just trying to sell themselves are not people you will read the blog of or converse with at a party (sometimes people who are just trying to sell their book/themselves will corner you at a party, and you just have to subtly shuffle away, saying 'of course! we'll catch up for lunch!').
3. Do not pay any attention whatsoever to awards and short-lists. You will likely only be continually disappointed. You write the best book you can, you send it out into the world, beyond that point it is out of your control. People will tell you if you get nominated or long-listed. Don't fixate on these things, because missing out ultimately does not matter all that much.
4. Just keep moving forward. Continue writing! Never stop! When you get distracted by bad reviews or not being long-listed or not selling well enough, you are probably not being very productive. If the selling and promoting parts of writing are what you enjoy most, get a job in marketing! If the writing is the most important, then that is what you should be doing. It is too easy to get caught up in promoting the book/yourself and not actually produce new material.
5. Get used to self-doubt and always yearning. I don't think there is a point at which a writer suddenly feels like a real writer, and the self-doubt disappears and one stops yearning for more success/more money/another book deal/an award. I think it's easy as an unpublished writer to assume the recognition of publication will change everything, and it's still easy as a newly published writer to assume a bit more success will instil self-confidence in you. I think these negative emotions associated with being a creative person (I don't know whether  people in more practical professions experience self-doubt, we shall have to ask them) are very useful to writing. Deal with the fact that you may never see a day when writing becomes easy, or you like your own work, or you feel you are a 'real writer', and keep producing new material despite it.
6. Stop comparing. Right now. Right this very second. Support other writers. You are really not their direct opponent. All you can do is produce your own best work. Someone else getting a six-figure deal has nothing to do with you. Someone you know winning an award or getting on a best-seller list does not make you any less of a writer. Be happy for other writers' success. But don't focus constantly on these markers of success. There is value in writing, even if you don't make a fortune out of it. You are not less-than any other writer. Your writing is unique and deserves to be read just as much as anyone else's.