Getting It Done

I set myself a deadline to submit a book manuscript for a competition at the end of this month.
I have started the book and have two more chapters to complete it and I don’t want to give up on this goal.

The past two weeks I left my brain unmanaged when it told me repeatedly that what I wrote is not good enough, that it’s too hard, that I have no inspiration, etc.
The more I waited, the harder it seems to resume the writing and complete it.

I start each morning with “I should be writing at least this many pages and get it done already” but this thought feels awful. It makes me resent this and not follow through.

I want to give myself this gift of finishing it on time and submitting it to the world and I keep spinning, trying to find the right thought that will get me motivated.
Perhaps you can suggest thoughts that will not be ‘Should… already’ kind of thoughts?