Among the worst despairs someone can have, one is called The Blank Sheet Desperation. It's the state of despair one faces in front of a blank sheet. It's because the person has all the ideas and has to start writing. The person has to have all the main ideas in order to begin. And how to encode correctly the ideas? Think of all the models that are isomorphic to the ones in your head.
This fear is similar to The Student Nightmare. The Student Nightmare is a dream like this: the student is in the classroom and doesn't remember there was a test. And then he/she gets The Test, and he/she knows no answer. It's a terrible nightmare. I read somewhere that it is The Student Nightmare because it happens to all students and there's no other nightmare that compares to it.