Writing has to be one of the most difficult pursuits. Its solitary. Its a lot of head banging and staring at a jumble of letters trying to force them to have meaning. Writing is also full of terror, at times, insurmountable terror.
These periods can be devastating for any author. The seemingly endless edits where grammatical and punctuation errors seem to breed like rabbits. Or perhaps the first draft that just won't translate from head to screen.
First, take a deep breath. Most of the time, the deadlines we have imposed, are by ourselves, and therefore will not suffer from a lost day or two. Take time to think about why you are writing. What is it that makes you sit down to laptop or paper and write? Do you enjoy it? Good. Keep going.
Secondly, after you have found perspective, forget what 'everyone else is going to say.' If you've published the book on Amazon or Barnes and Noble and you've found errors, take a breath. Every book has errors. Have a cry or shake your fists at the sky in frustration and then fix them. Go back and do it. You'll be so much happier.
Thirdly, get out of your own head and find someone to share the day with. Writers often forget that it is from the real world that we draw inspiration that feeds our imagination. We cannot have one without the other. Perhaps you see, like me, a homeless man with a sign stating, "Rogue ex-CIA agent seeking $ to get out of town." Now...isn't that a story.
At the end of the day, insecurities keep us from our dreams. In the immortal words of Suzy Kassem, "Doubt kills more dreams than failure ever will."
So go on. Focus on your writing. There's never been a better time.