I like this quotation from Douglas Adams's the Long Dark Tea-time of the Soul — "Words used carelessly, as if they do not matter in any serious way, often allowed otherwise well-guarded truths to seep through." —because it can be insightful in two ways.
The second and more prudent to writers, though, is the benefit that can come from free writing. Can't find your muse? Just sit down, look at something on your desk our outside your window, and start writing about it. Write randomly, throwing your words onto the screen "carelessly, as if they did not matter in any serious way." Such an exercise can reveal a truth to you:
That you do have something to write about.
That's Thor, by the way, in the picture. If you don't know anything about Adams's TLDTOTS, the pairing of the image and quotation probably makes no sense. Learn about it by reading, first, Dirk Gently's Holistic Detective Agency and then TLDTOTS, which is a sequel.
And thank you, Marvel's marketing machine, for making it so difficult for me to find an image of Thor that wasn't Chris Hemsworth.