A self-edit should have you cutting what doesn't add to your written work. Strive for simple, effective construction of phrases to achieve a better final product.
Interviewing a source can be an exciting part of your research, but the prospect of an hours-long transcription job can be a barrier to starting the writing process. Transcription software might be the answer you're looking for.
You may think your manuscript is ready for publication, but are there holes in your story? A beta reader can help determine if there's still work to do.
Being a writer, rather than someone who dreams of being a writer, is a challenge. Insecurity can be the twin of creativity — give yourself permission to just get started.
Life is short. Life is busy. How can you possibly add writing that book you to your stacked schedule? It starts with a commitment. To finish writing a book, you need to get started.
Do a slow read of your writing. Have you chosen your words well? Is your mind jumping ahead because the text is perfected or because you could cut it and lose nothing? If you don't want to read those words, will anyone else?