Sometimes the words and ideas flow effortlessly. More often than not you need an inspirational kick in the ass.
When I joined Nanowrimo for the first time in 2009 I had less of a lackluster experience. I diligently went to my keyboard every night tapping away until I got to my 1700 words.
The writing was crap. My plot flailed wildly and my characters didn't stay consistent. By mid-November I had little motivation to finish.
I continued to write.
I'd like to say that exercise had a happy ending and what I wrote in November 2009 became an excellent book with engaging characters. Truth is after Nanowrimo (which I didn't win) I left the book unread on my computer for months.
Then in October I revisited the idea and thought of an even better book than what I originally struggled with. Now I'm rewriting the book that once seemed to have so little promise. The story and characters (after months of letting my imagination subconsciously tinker with them) are much better. There still is a lot of work that needs to be done, but if I hadn't taken that crazy leap into writing in Nanowrimo I still would not have a book to work on.
The hardest thing is to delve into the unknown, sit your ass in front of the keyboard and write something, anything even if it seems useless at the time because you never know where that idea might lead.