I would choose to rewrite my first novel, The Veil of Time. As I read through it now, my mind develops additional storylines that would work well with what is already there. To work around this, because I'm not going to rewrite it, I will take those new storyline ideas and write new books from them.
Over the years, as I wrote my first book, I tried out various processes in order to learn which is most comfortable for me. After publishing my first book, I new exactly what process I use, AND I also knew what did not work for me. I think the most important thing a new author can do is to test out different writing processes. Don't stress out over it if you don't know right away what works for you. It's a learning experience. Take the opportunity to teach yourself.
Don't rush. There is so much that goes into writing a book. You can't possibly think about and take care of everything at once. If you try to do that, you won't get anything written. What I recommend is to list everything you need to go over, then go over each item one at a time.
Well thought out characters is essential to any piece of good writing. You want your readers to "spend time" with your characters by coming back to your books often.
Also, having a good character arc for your main character is what carries the story, so make sure you have that well thought out.
When I was a young preteen, I read a short story written by my oldest sister. It hooked me, and I wanted to write just like her. So I credit my inspiration to her.
I started actively writing in high school by writing short stories, and then I moved on to poetry. I gradually worked my way to writing books.
Don't sweat it. Don't rush. Learn as you go. Take your time and enjoy the process. Yes, there will be down time when you feel like you just are not able to do it. When you start to feel this way, stop and clear your mind by doing something else. This will free up your mind to work in the background without you worrying. Then, when you go back to your writing, you will be pleasantly surprised at how well you will do.
Don't edit as you go, or you won't get anything written. Trust me on this. Just write. There will be plenty of time later to edit.
Talk to other writers. You'd be surprised at how much that helps to release stress and tension.