One of my favorite ways to de-stress is to curl up in bed with a good book. Sometimes, I also go to my favorite coffee shop, find a seat in the corner and read while having a cup of coffee. I also do basic yoga poses or go out for a walk in order to get my mental house in order.
The first thing I do when I start feeling a build-up of stress is to pour myself an icy glass of water, drink it down, and feel the cold inside. It helps me refocus. Then, if I am at home, I take ten minutes to lay down with my eyes closed and try to think of something besides the thing that is bothering me. If I am not at home, I try to at least take a couple minutes to myself to gather my thoughts.
I like to get out and go for a walk. If I'm out in the fresh air breathing, moving, I can usually start to feel better right away. I also like to stretch a little bit as well. You'd be surprised how stretching a little bit relieves plenty of stress.