Problem one, and problem two

The first is not starting. You know what to do, you have the time blocked out, you sit down, and somehow it is four hours later and the file was never opened. The work is not hard once you are in it. Getting in is the whole difficulty.

The second is going blank. You prepared. You knew this material on Thursday. You sit down in the hall, your heart goes, your mind fills with commentary about how badly this is going, and the thing you knew is behind glass.

You can have both. Plenty of people do, and the second one often produces the first one. But they are not the same problem and they do not have the same answer, so it is worth knowing which one is eating your week.