Stop What You're Doing and Breathe
For a little aided meditation, there are several web environments dedicated to providing relaxing sounds and images. You may want to try http://www.calm.com/, which simply lets you into a quiet scene and stay there. If you press start, there will be a slow voice giving you directions, but you don't have to press start. You can just sit and breathe and watch the scene. You can also click on "no guidance," which will turn on quiet music in the background, and make the directions window disappear.
What do you do at this time of the academic year for a break? And what ends up happening if you don't take one? Whatever your answers are, I hope you manage to stop between work sessions and find a few moments of peace.