Decide your strongest and your weakest areas. Leave those, the one is into diminishing returns on effort, the other is too late to get on top of.
For some of the remaining fair-to-middling bits write down in note form and without looking it up, what you know, also in relation to likely type of questions. Then look at the book or previous notes, your mind will have been activated by the exercise, and hopefully bits of jigsaw will fit into place.
Go on to something else and do the same thing. At some time come back to the first subject and do the same as before, you'll find you're better than before but some things will have eluded you. They will now fix themselves better in your mind. You only have time to do that max. 2-4X in 2 days but it should help, and also stop the panic.