Depends on how long you have to de-stress. If you're talking about minutes or hours I always find some music relaxes me. I also like lighting some incense sticks. If you have longer just take some time for yourself. Sounds stupid but just do all the things you want to do that aren't work related. So kick back and watch TV, go visit a friend, take a walk, play a video game etc. The most relaxing vacation I ever took was when left my mobile and laptop at home. We rented a cottage in Wales in the UK and it was heaven. Absolutely no work for a whole week! I should also add that sometimes, just sitting and thinking works wonders. I personally am always so busy with things that I rarely get chance to just sit and think without having to click something or show someone how to create a database etc. When I do get to just sit and think it's very refreshing.
When I'm really stressed I like to work out. The harder the work out the better. It helps me relax and makes me tired enough so I can sleep instead of stress about things in the middle of the night!
When i was very tired,there is one word come into my mind,that is "Music",i think only music can help you out,take a try mate.