Came across this today in an old article in The Sunday Times: "Isaac Bashevis Singer wrote for more than four decades on an Underwood portable. For him, his machine was a kind of first editor. “If this typewriter doesn’t like a story, it refuses to work,” he said. “I don’t get a man to correct it since I know if I get a good idea the machine will make peace with me again. I don’t believe my own words saying this, but I’ve had the experience so many times that I’m really astonished. But the typewriter is 42 years old. It should have some literary experience, it should have a mind of its own.”
I once had a pencil which would write only brilliant sentences. Trouble was ... it did not allow me to write anything at all (in either German or English). So I threw it away. I haven't had much trouble with writing since then.