UPDATE: As of December 20th, 2017 I am back to accepting new assignments. I have submitted my latest book proposal.
ORIGINAL POST: For the first time I am turning down work. To get my book proposal done I can not accept any new assignments. Has this problem happened to you? It is a very uncomfortable position to be in.
The group I am turning down has been good to me and I have enjoyed working for them. But I have two sample book chapters to complete by January 2d and I will not get them done unless I apply myself. Already I am thinking I may need another week to finish.
I don’t know if this will permanently wound me with this employer. I hope not but I will understand if it does. This is all  unsatisfying in that the book proposal is purely speculative, perhaps some money in the distant future, while the company I am turning down pays promptly at the end of every month.
Have any of you had to deal with this problem and how did you manage?