Try smiling, studies have shown that the simple act of smileing can actually release endorphins and pleasure neurotransmiters that improve mood.
Also, laughing is a great release. Try this, in a very stressful situation break into a really wide grin, like crazy wide. Think about how silly you look to everyone else, then think about how inappropriate it is to be grinning so much when you have such serious problems.
This will initiate a giggle loop, (where the inappropriatness of your laugh makes you want to laugh harder, and the thought of how inappropriate each larger laugh causes you to eventually explode with laughter)
Once you are laughing you can sustain it for a long time by varying the pitch and style of your laugh.
For example, varying "he he he" and "ho ho ho" together sound so stupid it can't help but make you laugh all the more.
With such a cornocopia of possible laugh styles you can really explore the richness that is laughter and frivolity, and remember that the more stupid a laugh sounds, the funnier it is, thus causing more laughter.
AND because of mirror neurons, laughter is contagious.
Once, in a library, when me and 3 friends were supposed to be working on a project, I started laughing because it suddenly popped into my head how inappropriate it would be to laugh out loud at this moment. (giggle loop) That thought made me snort and laugh quietly which caused my friends to do the same.
This resulted in a chain reaction that ended with all 4 of us roaring with laughter, over the simple fact that the other 3 were laughing.
We were kicked out of the libary because we couldn't stop laughing. The more the librarian screamed at us the more we laughed!
By the time we stopped we all felt very relaxed and happy.
So give that a try sometime, smiling and laughter.
