Why not try this 10 min mindfulness practice to calm you down and give you a break from your revision? To enable you to return to it revived and refreshed.  You may even find that you can use it in other areas of your life too. http://franticworld.com/mindset/ You don't need anything special.  As the website says: 'You will need:  a Chair; a Body; some Air; your Mind. That’s it.' Give it a try!