It was a rare moment when Dylan sat still to talk with Ed Bradley, who asked him how did he write that stuff. Bob recited a couple of lines from "It's Alright, Ma" and said he didn't know how he wrote that song or so many others. They came from some "magical place" and he confessed he could never write that way again. I think for a lot of creative people they are briefly on fire. The Beatles were amazing but when they split up the fire went out. Dylan has always conjured some excellent music. Blood on the Tracks happened 10 years after "It's Alright, Ma" and that was a fine piece of work, but he was never on fire ever again.
http://tinyurl.com/cyv6wg5

Different kinds of fire at different times.