Must-Reads--Yours, Mine, and Ours discussion

I won't give any of the main plots points away; however, I think this is what happens when you have a really, really creative book idea but limited time to execute it well due to a deadline, or your interest in writing it wavered after 50 pages. Trust me, I have started out deep-fried turkey hot on an idea just to spend months not adding another word to my "masterpiece." So, tell me, "goodread"ers who join this group, how do you overcome your lack of writing motivation (writer's block does not exist; writers lack the motivation to write, which is what stops him/her from writing not some mental or physical obstruction), and when you read a book with a disappointing ending, or a lot of loose ends, what advice would you give the writer?