Probably (1) my imagination and (2) the amount I read.
No, sadly, because although I use both all the time, I am not getting the stuff down on paper. However, I have read a couple of books that help greatly. One of them is by Peter Elbow. His book, "Writing with Power" contains useful information on free writing and other techniques to get you doing something. Another useful resource is The Artist's Way. It's a long time since I read that book but it is helpful for overcoming writer's block, IF you go through and do the exercises. It uses journalling as a way of getting you writing.
I find it very useful to answer questions, because I can easily think of a means of answering many questions and writing it down, whereas, thinking of a particular subject to create something on is more difficult - there is such a WIIIIIDE choice!