I also have the problem (possibly the point of workshops is to fix these problems, but I feel it would reduce the usefulness of one for me) of being very bad at writing on demand. My inspiration is very random. And sure, I write a lot of good stuff, but if you sat me down and told me to write six pages of SOMETHING then maybe I could and maybe I'd manage three terrible sentences. Depending on whether I had words at the time or not.