Laughing is good for you, try and do as much of it as you can! You can get courses in how to laugh more, but I prefer a good dose of comedy. There is a comedy night at our local arts centre about once a month and I regularly cry with laughter - and these are comedians who haven't even made it onto TV!
If you can't get out to a comedy night, maybe you could rent a funny movie, you could get some stand up from Eddie Izzard or a Ben Stiller film. Or even something by Adam Sandler (if that's waht makes you laugh..) the choice is yours. Me and Lena are renting the dvd box set of all the Seinfeld shows (one at a time) and they are hilarious! Don't be gloomy about your own circumstances, laugh at somebody elses for 20 minutes.
If you don't have a TV you could go to your local library and get a book of jokes. Here's one: what do you get if you cross a kangaroo with an elephant? Great big holes all over Australia! That made me laugh just typing it - and I knew the answer! Got a favourite joke? Email it to us and maybe we can make our own joke book.
Laughter releases tensions that we store up in our bodies, yoga releases the same tensions through breathing exercises that loosen the diaphram, I can reccomend Yoga, but if it's not your style, try to make time for comedy.
Laughing is good for you, look at the lighter side of life, lighten up and count your blessings.