The Internet is packed with good advice for authors-in-waiting, but I would like to add this: find a support group. Other writers are your friends, and unless you have an obsessive-compulsive family member, they are the only people who will understand your pre-publication / post-publication terror.
Reach out to other writers; support them and they will support you. Network with unpublished writers in your genre, go to debut authors’ events, contact authors you admire. Join online groups with other writers—start your own!—and remember, writers are also readers and reviewers.
Writing may be a solitary process but publishing a novel is not. Find a tribe. You’ll be glad you did.
If you would like me to meet with / talk with your writing group, please contact me at firstname.lastname@example.org
Blogging about the writing life: