Take your breaks! Whether you get timed breaks, paid or unpaid- you have to force yourself to take the time out. Don't think of it as 15 minutes that you could be calling a customer, but 15 minutes that you NEED to recharge yourself.
Step2
If you drive to work, go sit in your car. The cleaner the car- the better. Remember- a cluttered car (or desk or house, or whatever) means a cluttered mind. Meditation is all about clearing your mind, if only temporarily. During your break- remove yourself from your desk and from all of your co-workers. Taking a break to complain about work IS NOT taking a break!
Step3
Sit in your car. Depending on weather- you can have windows up, down- however you feel comfortable. If you have the time, a change of scenery helps- even if it mean driving to a remote corner of the parking lot. Sit still with a straight back. Close your eyes and breathe in slowly through your nose. Be aware of your breath and focus ONLY on inhaling and exhaling. By focusing your mind on your breath- you let your mind be active, but without thinking about anything work related.
Step4
If you want- you can try a simple mantra (a repeated chant). Some easy mantras are "Om" (ohm), or "Om Shanti" which means peace. Repeating one of these over and over gives your busy mind something to do while your body melts into relaxation. If you don't feel comfortable saying these out loud- you can repeat them in your head. Pick one mantra and repeat it as many times as you feel comfortable.
Tips & Warnings
remember to take this time for yourself every day. Know that there will be work for you when you get back to your desk- there's nothing you can do about that, but you'll deal with it in 10- 15 minutes. By the end of the day- the mind is stressed from everything it has been through, this helps you "restart" your day by giving yourself a clean slate to work with.
Enthusiast 
