Seinfeld did a Reddit AMA ("Ask Me Anything") and told a bunch of great stories about the making of Seinfeld and Comedians in Cars Getting Coffee (which is one of the best things on the internet right now). All the answers are worth reading through, but the best of the bunch was this one:
Q: “How do you deal with writers block?”
A: “Writer's block is a phony, made up, BS excuse for not doing your work.”