If it's mental stress, I have found that helping others less fortunate than I am does my head a lot of good. It doesn't have to be something big; hold the door for the older lady at the library, smile at the postal clerk, say "hi" to a stranger on the street, so long as he doesn't look like Godzilla.
Exercise helps a lot, too. There is something very nice about leaving the house with music (or without if you prefer), knowing you are going on a couple of mile walk and you will feel better when you come home.
Being nice to your significant other, even if you don't feel like it. In other words, the less you think about you, the more other people will think about you. My mom always said I paid wayyyyyy to much attention to my internal life and not enough to the business of simply Getting On With It. I probably did at the time.
I in no way am trying to minimize your stress; that stuff'll make you crazy, but when in doubt, A Good Walk will often help considerably. And if you are really stressed, you can just keep walking (my gentle attempt at humor).