Hahaha, yeah. That's how I feel about the book I am writing right now. I have all the pieces in front of me, but when i try write it down my mind goes blank and I can barely manage to write a sentence. Then suddenly my brain thinks of an AMAZING idea that could be an awesome book but i can't make it because i'm writing TRLOA and I would start getting my ideas jumbled. Then my brain would think of another idea and it would end up a cycle with about 100 books that are not completed.
And then you can't put the idea in your other book because you feel like it's a completely different story line!!! lol
Sorry, i'm rambling x :P