Yes, I have a thousand tongues,
And nine and ninety-nine lie.
Though I strive to use the one,
It will make no melody at my will,
But is dead in my mouth.
From Stephen Crane's collection The Black Riders and Other Lines, better known for the lines, "because it is bitter, and because it is my heart," which also came to mind today for a silly reason on Facebook.
In other words, sometimes the magic works, sometimes it doesn't. But you keep typing...and hope it returns.