When you wake up, here's what you do: FORCE YOURSELF to sit in front of the TV, watch funny videos, or play games, or do something that has nothing to do with studying for finals, for AT LEAST ONE HOUR, no less. Then, the time you do spend studying will be used more efficiently. You'll find that, even with an hour break, you'll still have spent less time overall because you allowed yourself to recover some brain power. You'll also work off some stress that way.
Also, make sure you've eaten something nutricious this week. Surviving on salt, sugar, and ramen alone tends to aid the process of brain mushification.